|Kor, a Klingon male (2267)|
|Sirella, a Klingon female (2374)|
"A Klingon's honor means more to him than his life!"
The Klingons were a humanoid warrior species that originated from the planet Qo'noS (pronounced Kronos), an M-class planet. One of the major powers of the galaxy, the Klingons were a proud, tradition-bound people who valued honor and combat. The aggressive Klingon culture had made them an interstellar military power to be respected and feared.
History and politics
- Main article: Klingon history
The Klingon Empire was founded some time in the 9th century by Kahless the Unforgettable, who performed many heroic feats including the unification of the Klingon people when he killed the tyrant Molor. Kahless came to be revered in Klingon society to the point of near-deification, and many aspects of Klingon culture came to revolve around an emulation of Kahless' life. (TNG: "Rightful Heir")
The warrior ethos had been an important aspect of Klingon society since the time of Kahless, but the warrior aspects became much more dominant beginning in the early 22nd century. Previously, Klingon society was regarded as socially balanced, but over time, the warrior caste gained greater prominence, to the point where the Klingons widely came to be regarded as a "warrior race." (ENT: "Broken Bow", "Judgment")
Because of their aggressive outlook, the Klingons generally had poor relations with other races, after they began to move out into space. Because the worlds of the Klingon Empire were resource-poor, the Klingons developed an intense belief in the need for expansion and conquest in order to survive. The Klingons' relationship with Humans and the Federation was rocky at best. Following the disastrous first contact between Klingons and Humans in the Broken Bow incident, tense rivalries and unavoidable conflicts often developed between the two races. (ENT: "Broken Bow"; TNG: "First Contact")
In the year 2154, the Klingons gained access to the genetic material of Human Augments and tried to adapt this genetic engineering to improve themselves. The test subjects did gain increased strength and intelligence, but then, their neural pathways started to degrade and they died in agony. One of the subjects suffered from the Levodian flu, which was modified by the Augment DNA to become a fatal, airborne, mutagenic plague that spread rampantly through the Empire, from world to world. In the first stage of this plague, Klingons lost the ridges on their foreheads and began to look more Human. With the help of a Klingon scientist named Antaak, Dr. Phlox of the Earth starship Enterprise was able to formulate a cure that halted the genetic effects of the virus in the first stage. This retained the changes in appearance, along with some minor neural re-ordering. The neural ordering caused changes in the emotional make-up of the Klingons. For example, the infected started to feel fear. Even though the infected did not develop any stage-two characteristics – such as enhanced strength, speed, or endurance – they did not die from it. This left millions of Klingons changed. These alterations were even passed on to their children. (ENT: "Affliction", "Divergence") From the 2270s onward, Klingons encountered by the Federation had their forehead ridges restored. (Star Trek: The Motion Picture)
Klingons were apparently so embarrassed by the fallout from their failed attempt at genetic enhancement that they refused to discuss the incident with outsiders. Due to the secrecy of the Klingon Empire, knowledge of the change became lost over time to the general population of the Federation. By the 24th century, the reason for smooth-forehead Klingons was not widely known outside the Empire, and questions were generally met with a brusque answer along the lines of, "We don't discuss it with outsiders." (ENT: "Affliction", "Divergence"; DS9: "Trials and Tribble-ations")
By 2223, relations between the Federation and the Klingon Empire degenerated to a point of relentless hostility, which lasted for several decades. (Star Trek VI: The Undiscovered Country; TNG: "First Contact")
The lingering tensions between Klingons and Humans continued to rise, eventually leading to the Battle of Donatu V, near Sherman's Planet in 2245, and later erupted into what was considered the Federation-Klingon War of 2267. This war was quickly ended by intervention by the Organians, after only four days of fighting. (TOS: "The Trouble with Tribbles", "Errand of Mercy") Over the next several decades, an uneasy peace developed that was broken by brief but fierce skirmishes and conflicts (Star Trek III: The Search for Spock; Star Trek V: The Final Frontier). A true and lasting peace finally came in 2293, with the signing of the Khitomer Accords, thanks to the efforts of Chancellor Gorkon and the Human Starfleet officer James T. Kirk. (Star Trek VI: The Undiscovered Country) Since then, despite several periods of rocky relations (see Federation-Klingon War (2372-73)), the Federation and the Klingon Empire have been steadfast allies, especially in the face of Dominion aggression in the 2370s. (DS9: "By Inferno's Light")
The Klingon relationship with the Romulan people was also extremely unstable. A short-lived alliance and technology exchange notwithstanding, the Romulan Star Empire was typically regarded by the Klingons as a "blood enemy" since at least the 23rd century. Sporadic Romulan attacks against Klingon colonies (see Khitomer Massacre) and interference in Klingon affairs (see Klingon Civil War) continued to sour relationships between the two peoples. (TNG: "Sins of the Father", "Redemption II")
In the alternate reality, in 2233, the crew of the USS Kelvin briefly considered whether a particular lightning storm effect, observed by the Kelvin near the edge of Klingon space, might be Klingon in origin. This possibility was discarded by Starfleet. The phenomenon preceded the arrival of the Romulan mining vessel Narada from the prime universe. An armada of 47 Klingon warbirds was attacked and obliterated by the Narada in 2258. (Star Trek)
By 2259 in the alternate reality, after first contact with the Empire, the Klingons had conquered and occupied two planets known to the Federation and fired on Starfleet ships half a dozen times. Tensions between the two powers were high and an all-out war was considered inevitable. During that year, before surrendering to the Federation, Khan Noonien Singh destroyed three D4-class patrol ships on the Klingon homeworld, as well as killed the crews of the vessels. (Star Trek Into Darkness)
"Even half drunk, Klingons are among the best warriors in the galaxy."
Klingon society was extremely complex. Before its decline in the mid 22nd century and again in the late 23rd century, Klingon society was based on a feudal system organized around traditional Great Houses of noble lineage, to which various parts of the population owed fealty. The Great Houses are traditionally represented in the Klingon High Council, which is led by a Chancellor.
The decline of Klingon culture is demonstrated in the acts of the Klingons themselves. They stopped caring about their weapons to the point that they let them rust (ENT: "Marauders") and even stopped caring for true honor. (ENT: "Judgment") Sometime after the augment virus took hold of the Klingon Empire, a new regime took control, turning the Empire into an authoritarian state that kept tabs on all who served. (TOS: "Errand of Mercy") The old ways returned in the latter 23rd and early 24th centuries respectively.
Males traditionally dominated public life in the Empire, assuming the leading roles in politics and the military with only rare exceptions. (TNG: "Redemption") A notable exception to the prohibition of women serving on the High Council came when Azetbur became Chancellor of the High Council after her father, Gorkon, was assassinated in 2293. (Star Trek VI: The Undiscovered Country) Women, in turn, traditionally dominated the household and the management of the family's affairs. (DS9: "You Are Cordially Invited") Klingon women were treated as equals, except in politics and matters of inheritance. They were prohibited by law from serving in the High Council and could not take control of their Houses unless they had the money and no male successors of the lineage. Otherwise, Klingon women were expected to exhibit the same physical prowess and lust for blood and honor as the men.
Klingon society functioned through a system of family reputation and honor. Tradition was an integral part of their lives and breaking from observances was considered a grievous insult to society, an insult not forgotten easily. An offense usually brought shame to the offender's name for several generations. The highest shame was discommendation, an action by the High Council to officially strip a Klingon of his personal or family honor. Bloodlines and relations were also taken very seriously by any "true" Klingon. Lines comprised more than mere family members. (TNG: "New Ground")
An integral part of tradition was the various rituals that marked milestones in a Klingon's life or the history of the Empire. Most notable of the rites was the Rite of Succession, which a future leader of the Empire had to complete with a valid Arbiter of Succession (Captain Jean-Luc Picard, in the case of Gowron) overseeing the proceedings. Before the Rite could begin, there was another elaborate ceremony needed to confirm the death of the previous leader. This was known as the Sonchi ceremony. (TNG: "Reunion") Individual Klingon warriors were expected to go through the Rite of Ascension to be recognized as a full adult. (TNG: "The Icarus Factor") If the house that an individual Klingon belonged to was dissolved or fell into dishonor, he could be adopted into another house through the R'uustai or alternative ceremonies that symbolically marked the joining of kinship and allegiance. (TNG: "The Bonding"; DS9: "Sons of Mogh", "Soldiers of the Empire", "Sons and Daughters")
The most distinctive feature of Klingon anatomy (except in those individuals afflicted with the Augment virus) was a sagittal crest, beginning on the forehead and often continuing over the skull. The cranium was encased in an exoskeleton, which possessed a feature known as the tricipital lobe. (TNG: "Descent")
On average, Klingons were larger and physically stronger than Humans, though they possessed a much lower tolerance for cold weather. (VOY: "Displaced"; DS9: "Change of Heart") Spock said, once, that Klingons lacked tear ducts; however, Klingon myth states that Kahless once filled the ocean with his tears, and at least one Klingon, Kurn, produced tears. (Star Trek VI: The Undiscovered Country; TNG: "Birthright, Part II"; DS9: "Sons of Mogh")
Internally, Klingon anatomy was markedly different from that of Humans. There was a great deal more multiple redundancy in their organs, a principle they called brak'lul. This allowed Klingons to survive severe injuries in battle. They had twenty-three ribs, two livers, an eight-chambered heart, three lungs, and even redundant neural function as well as multiple stomachs. Some geneticists believed that the extra organs, notably the third lung, evolved to give Klingons greater stamina on the battlefield. Klingons had relatively little knowledge of their own biology and their medicine was very poorly developed. This was largely due to their warrior traditions – a Klingon who was wounded was expected to be left to either survive through his own strength, die, or undergo the hegh'bat, a form of ritual suicide. (TNG: "Ethics"; VOY: "Lineage")
Despite the anatomical and physiological differences between Klingons and Humans, the two species had very similar nutritional requirements. Dr. Pulaski once noted that, while most Humans find Klingon food unpalatable, usually, "what kills us, kills them." (TNG: "A Matter Of Honor") However, the "tea" used in the Klingon tea ceremony seems to be an exception. (TNG: "Up The Long Ladder") Apparently, the tea concentrated some (unknown) toxic heavy elements found in the soil in which its plant of origin grew, synthesizing a poison deadly to Humans, and capable of seriously sickening Klingons, as it does.
Klingon pregnancies normally ran thirty weeks, but with mixed species, gestation times were shorter. The odds against Klingon-Human conceptions were rather high; however, when successful, Klingon and Human metabolisms sometimes clashed, causing biochemical fluctuations in the mother, which may lead to fainting. Klingon traits remained dominant for several generations, even with a single ancestor; therefore, a child even ¼ Klingon still possessed forehead ridges, if he or she carried the gene. (VOY: "Lineage")
Klingons had ridged spines, chests and feet. (TNG: "Ethics"; DS9: "Sons of Mogh"; ENT: "Broken Bow") After birth, some Klingon infants experienced a pronounced curvature to the spine, a form of scoliosis, which was correctable by surgery. This "defect" tended to run in Klingon families, especially among females. Federation medicine, fortunately, advanced beyond that, allowing an additional choice of treatment involving genetic modification. (VOY: "Lineage")
Klingon children matured far more quickly than Human children. At the age of only one Earth year, a Klingon child had the appearance a Human child had at about four. By the age of eight Earth years, a Klingon attained the maturity a Human did not reach until about age sixteen. (TNG: "Reunion"; DS9: "Sons and Daughters") When Klingon children began growing into adults, they went through jak'tahla, a Klingon form of puberty. (Star Trek: Insurrection) Like other mammalian species, Klingon females were capable of lactating to breast-feed infants. (TNG: "A Matter Of Honor")
Klingons such as Kurn had the instinctive ability to sense the decision to kill by looking into the eyes of their opponents. (DS9: "Sons of Mogh") Worf did not have this ability, probably due to the fact that he was raised by Humans on Earth.
Religion and tradition
- See also: Klingon wedding
Ritual was a very important element in Klingon society. While the Klingons were not a religious people as such, they did believe that deities existed at one time. However, Klingon warriors supposedly slew their gods, as they were considered to be more trouble than they were worth. (DS9: "Homefront")
Once a Klingon died, the spirit was considered to have exited the body, leaving behind a worthless shell to be disposed of. (VOY: "Emanations") In the Klingon death ritual, it was traditional for those on hand to howl into the sky, as a warning to the afterlife that a Klingon warrior was about to arrive. (TNG: "Heart of Glory"; DS9: "Tears of the Prophets") In some cases, a funeral dirge was sung in memory of the deceased, or friends sat with the body to protect it from predators, a practice known as ak'voh. (DS9: "The Ship")
Furthermore, a Klingon who was unable to fight, and hence unable to live as a warrior anymore, had the traditional obligation of committing the hegh'bat, which was the Klingon ritual suicide. Tradition dictated that the eldest son or a close personal friend must assist. That person's role was to hand the dying Klingon a knife so that he could plunge it into his heart, remove it, and then wipe the blood on his own sleeve. (TNG: "Ethics")
The Klingon afterlife was supposedly divided into two branches. The dishonored were taken to Gre'thor aboard the Barge of the Dead, a vessel captained by Kortar, the first Klingon. Kortar was supposedly the one who had originally killed the gods who created him and was condemned to ferry the dishonored to Gre'thor as a punishment. Once in Gre'thor, the dishonored were watched over by Fek'lhr, a vaguely Klingon-esque figure. While it may be tempting to view Fek'lhr as the Klingon equivalent of the Human devil, according to a statement made by Kang, the Klingons had no devil. (TNG: "Devil's Due"; VOY: "Barge of the Dead"; TOS: "Day of the Dove")
Those who died honorably supposedly went to Sto-vo-kor, where Kahless was said to await them. However, should a noble warrior die in a manner that might not merit a place in Sto-vo-kor, such as being assassinated in a surprise attack, he may still earn a place, if others dedicated a great battle to his name, thus showing that he had earned respect among the living. (TNG: "Heart of Glory", "Rightful Heir"; VOY: "Barge of the Dead"; DS9: "Shadows and Symbols")
Klingon rituals included the R'uustai, a bonding ceremony which joined two people together in a relationship similar to brotherhood. (TNG: "The Bonding") Klingon tradition holds that "the son of a Klingon is a man the day he can first hold a blade." (TNG: "New Ground")
If a Klingon warrior struck another Klingon with the back of his hand, it was interpreted as a challenge to the death. Klingon warriors spoke proudly to each other; they did not whisper or keep their distance. Standing far away or whispering were considered insults in Klingon society. (DS9: "Apocalypse Rising")
When going into battle, Klingon warriors often sang the traditional warriors' anthem, which was essentially an invocation to Kahless and a pledge to win a good death in battle. (DS9: "Soldiers of the Empire")
When choosing a mate, it was traditional for a female Klingon to bite the male's face, allowing her to taste his blood and get his scent. (VOY: "Blood Fever") Worf once told Wesley Crusher that, per Klingon mating rituals, "Men do not roar. Women roar. Then they hurl heavy objects. And claw at you." Of men, Worf said, "He reads love poetry. He ducks a lot." (TNG: "The Dauphin") Klingon daughters traditionally were given a piece of jewelry called a jinaq when they became old enough to select a mate. (TNG: "Birthright, Part II")
Science and technology
Food and beverages
- Bregit lung
- Grapok sauce
- Heart of targ
- Klingon martini
- O'mat Gri T'M pffiots
- Pipius claw
- Rokeg blood pie
- "Hide and Q" (Season One)
- "Heart of Glory"
- "A Matter Of Honor" (Season Two)
- "The Icarus Factor" (holograms only)
- "The Emissary"
- "Shades of Gray" (archive footage only)
- "The Offspring" (hologram only) (Season Three)
- "Sins of the Father"
- "Reunion" (Season Four)
- "Future Imperfect" (illusion only)
- "The Drumhead"
- "The Mind's Eye"
- "Redemption II" (Season Five)
- "Unification I"
- "Unification II"
- "New Ground"
- "Cost of Living"
- "Imaginary Friend"
- "Rascals" (Season Six)
- "A Fistful of Datas"
- "Birthright, Part I"
- "Birthright, Part II"
- "The Chase"
- "Rightful Heir"
- "Gambit, Part II" (Season Seven)
- "Preemptive Strike"
- "Past Prologue" (Season One)
- "Dramatis Personae"
- "Invasive Procedures" (Season Two)
- "Playing God"
- "Blood Oath"
- "The Maquis, Part II"
- "The House of Quark" (Season Three)
- "Through the Looking Glass"
- "The Way of the Warrior" (Season Four)
- "The Sword of Kahless"
- "Return to Grace"
- "Sons of Mogh"
- "Rules of Engagement"
- "Shattered Mirror"
- "Broken Link"
- "Apocalypse Rising" (Season Five)
- "Looking for par'Mach in All the Wrong Places"
- "Nor the Battle to the Strong"
- "Trials and Tribble-ations"
- "In Purgatory's Shadow"
- "By Inferno's Light"
- "Soldiers of the Empire"
- "Children of Time"
- "Blaze of Glory"
- "Call to Arms"
- "A Time to Stand" (Season Six)
- "Sons and Daughters"
- "Favor the Bold"
- "Sacrifice of Angels"
- "You Are Cordially Invited"
- "In the Pale Moonlight"
- "His Way"
- "The Reckoning"
- "Tears of the Prophets"
- "Image in the Sand" (Season Seven)
- "Shadows and Symbols"
- "Treachery, Faith and the Great River"
- "Once More Unto the Breach"
- "The Emperor's New Cloak"
- "Strange Bedfellows"
- "The Changing Face of Evil"
- "When It Rains..."
- "Tacking Into the Wind"
- "The Dogs of War"
- "What You Leave Behind"
- "Flashback" (Season Three)
- "Real Life" (hologram only)
- "Day of Honor" (hologram only) (Season Four)
- "The Killing Game" (hologram only)
- "The Killing Game, Part II" (hologram only)
- "Infinite Regress" (Klingon Borg)
- "Someone to Watch Over Me" (photo only)
- "Barge of the Dead" (dream only) (Season Six)
- "Unimatrix Zero" (Klingon Borg)
- "Unimatrix Zero, Part II" (Klingon Borg) (Season Seven)
- "Flesh and Blood" (hologram only)
First televised appearances
Klingons were introduced in Star Trek: The Original Series, making their first appearance in the episode "Errand of Mercy". They were originally meant to be involved in only that installment. (Star Trek Magazine issue 125, p. 37) The episode's writer, Gene Coon, was the person who initially imagined the species and their culture. However, both aspects were among multiple elements of the series which Star Trek Producer Gene Roddenberry joked originated from his "cousin in Ohio." (Inside Star Trek: The Real Story, paperback ed., p. 136)
Gene Coon primarily modeled the Klingons, metaphorically, on contemporary Russians, making the standoff between the species and the Federation representative of that between the Russians and the Americans during the then-ongoing Cold War. (Star Trek: The Original Series 365, p. 139) Dave Rossi clarified, "In many ways, the Klingons were born out of our fear, as Americans, of [...] the Communists." According to D.C. Fontana, there were a range of other real-world sources that additionally gave rise to Coon's creation of the Klingons. "What did he want to accomplish? I think he just wanted a good, tough villain... for Kirk," Fontana speculated. "And I think he was basing a lot of it on the kind of attitude of the Japanese in World War II, the Nazis in World War II, because Gene was a World War II veteran marine and he really took all this to heart. And as a result, he modeled them on the worst villains he knew." ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray) Chekov actor Walter Koenig specified, "They were evil and nationalistic. But Star Trek did not address the baser things in man. There was no imperialism or colonialism. We addressed this obliquely, hoping that someone would pick up our message out there." (Cinefantastique, Vol. 27, No. 11/12, p. 61)
After Gene Coon conceived the Klingons, a name for the species did not immediately come to mind. He took inspiration from a name which came into earshot, that of Lieutenant Wilbur Clingan – a friend of Gene Roddenberry who served with him in the Los Angeles Police Department. (Star Trek: The Original Series 365, p. 141; Star Trek Creator: The Authorized Biography of Gene Roddenberry, p. 131) Even when retired years later, Clingan was still proud to introduce himself as the first Klingon. Commented Robert Justman, "The question remains whether Gene named these creatures out of homage or revenge. I've heard it both ways." (Star Trek: Communicator issue 114, pp. 22-23) Also under dispute is the nature of the production staff's reception to the name. According to the book Star Trek: The Original Series 365 (p. 141), the series' production staff liked how the moniker sounded, which led to Coon altering the spelling and using it for the fictional species. However, D.C. Fontana stated, "We never liked the name. We said, 'Gene, can't you come up with a different name than Klingon? We hate it.' But we never [came] up with anything better, so we left it." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 40)
The script of "Errand of Mercy" introduces the Klingon look by saying, "We see the Klingons are Orientals," thereafter repeatedly describing them as "hard-faced." Indeed, the Klingons originally appeared as fairly ordinary Humans with heavy makeup as well as emboldened eyebrows, with some of the males having mustaches and goatees. The reason the Klingons were accepted as looking so Human-like, delineated from Humans mainly by their mannerisms and characters, was that the series had neither the materials, budget nor time necessary to create elaborate makeup for the Klingons. ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray)
Kor actor John Colicos was largely responsible for the Klingon head design. "I had never heard of Klingons in my life before," recalled Colicos. "I said, 'Oh, well, the makeup department is going to know exactly what it's doing.' When I arrived at Paramount the make-up man said to me, 'What in the hell does a Klingon look like?'" (Star Trek: Communicator issue 104, p. 19) Makeup Designer Fred Phillips started the design process by directly asking Colicos how he wanted to look. Despite thinking of the Klingons as the futuristic Russians they were intended to be, Colicos took inspiration from Genghis Khan, as Kor was likewise an ambitious military commander. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 40) "He thought that was a hell of a good idea," Colicos said, regarding Phillips' reaction to the concept. (Star Trek: Communicator issue 104, p. 19) Due to the Genghis Khan influence, Colicos proposed "a vaguely Asian, Tartar appearance," with an alien-looking "brown-green makeup." "Within two hours," said Colicos, "this thing emerged and that was it." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 40) Colicos was pleased with how he had influenced the layout of the makeup. "I thought I was pretty crafty [...] because it only took 20 minutes to put on," he said. (Star Trek: Communicator issue 104, p. 19)
The swarthy appearance of the Klingon faces was actually created with a dark brown cream base, which was applied to the actors' faces. (Star Trek: Aliens & Artifacts, p. 42) Rick Stratton, who was part of a small team of young makeup artists enlisted by Fred Phillips to work with him on Star Trek: The Motion Picture, uncertainly recollected, "I think the makeup was called 'Mexican #1 or #2.' That was the name of the original makeup foundation – they actually had kind of racist names at the time, like 'Negro #1' and 'Mexican #2' – which was the basis for the original Star Trek makeups." (Star Trek Magazine issue 172, p. 59)
The males' facial hair appliances were lace, glued on using spirit gum, and their eyebrows were made to look bushy. (Star Trek: Aliens & Artifacts, p. 42) Noted Michael Westmore, "They actually shaped and penciled in the eyebrows with pencil." (Star Trek: Communicator issue 110, p. 59) Due to the minimalism of the makeup used, the Klingons were easy to create, from a makeup standpoint, and were therefore able to be shown in groups.
As the makeup procedures for the Romulans were too costly for that species to be featured on a regular basis (despite the Romulans having been meant as an ongoing villain), the Klingons – much cheaper to create – replaced them as the show's chief antagonists. (Star Trek: Aliens & Artifacts, p. 42) "We didn't intend for them [the Klingons] to be running villains, but it turned out they were pretty easy to do," reflected D.C. Fontana. "They didn't have to have ears put on [....] And once we figured that out, the Klingons became regulars." ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray) "It didn't happen at first, but they were good villains," offered Robert Justman. "A lot of these things didn't enter my consciousness at the time, but looking back on it now, I can see how unerring Gene [Coon]'s instincts were." (Star Trek Magazine issue 125, p. 37) In agreement, Fontana described the ease at which the Klingons could be done as "the beauty of them." (Star Trek: Communicator issue 114, p. 22) She said further, "They became a very good adversary, because once you established them, you had to find out ways to explore them." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 40) However, Fontana personally found the Klingons less interesting than the Romulans.  Comparing the two groups, she stated, "[The Klingons] were interesting villains with an agenda, not quite as mysterious as the Romulans. The Romulans were a keepout group. The Klingons were operating in our territory which could lead to more direct contact–and conflict–with the Federation." (Star Trek: Communicator issue 114, pp. 22 & 23)
Gene Roddenberry was unsettled by the way Klingons were portrayed on the original series, coming to realize that they were at loggerheads with the ethos of Star Trek by being shown as entirely villainous. (Star Trek Monthly issue 10, p. 50; The Making of Star Trek: The Motion Picture, pp. 215-216) In 1980, Susan Sackett relayed about this opinion of Roddenberry's, "He believes that the Klingons emerged as too simply the epitome of evil – the bad guys who always wear black – whereas one of Star Trek's philosophical cornerstones was that there are many forms of truth, and other life forms (or other humans, for that matter) should not be branded good or evil solely on the basis of our own customs." (The Making of Star Trek: The Motion Picture, pp. 215-216)
David Gerrold wrote, "All of the Klingon episodes were, in one way or another, restatements of the original: Klingons and Earthmen must not fight." He also approved of the Klingons, if they were to be shown on a regular basis, as not engaging in all-out conflict with the Federation, saying, "Not only does this provide a good background for a wide variety of stories, both humorous and dramatic, but it is a lot more optimistic and (hopefully) believable than a space war. After all, a race that can achieve space travel is going to have done so only through large scale programs of social cooperation, and it is hoped, in the process will have learned that there are better ways than aggression to accomplish one's goals." (The World of Star Trek, 1994 UK ed., p. 32)
No specific rules were ever stipulated for writing about Klingons. "They had a certain culture and a certain kind of way of thinking that we didn't really line out in the bible or anything like that but we knew from past experience on other scripts how we had developed them," D.C. Fontana reflected. "So, if a writer was going to use them, we just let them read those other scripts or watch the episodes, so they could get a handle on it." 
It was David Gerrold who proposed reusing Klingons in "The Trouble with Tribbles", which was at that time a story entitled "A Fuzzy Thing Happened To Me...". The suggestion, later described by Gerrold as "almost accidental," was inspired by a statement made by Gene Coon, while he and Gerrold were seeking a villain for the installment. Gerrold recounted, "'The threat has to come from outside the Federation.' And when he said that, something went twang in my mind, something I'd seen on a first-season rerun – I opened my mouth, wondering what I was going to say, and said, 'Klingons!' [....] Perhaps the fact that I had just seen the episode the week before had something to do with it." Gerrold believed the Klingons fit perfectly into the story. (The Trouble with Tribbles, pp. 80-82) He subsequently asked Coon if he could reuse them as the alien menace required for the episode. ("The Trouble with Tribbles" audio commentary & Starfleet Access, TOS Season 2 Blu-ray) "He said, 'You know, we've been talking about having a continuing threat, a continuing nemesis for Kirk, and the Klingons are probably the best way to go,'" recalled Gerrold. ("The Trouble with Tribbles" audio commentary, TOS Season 2 Blu-ray) Despite Coon revealing that the producers had been discussing the option to have the Klingons become a recurring nemesis, he also mentioned that there hadn't been a suitable story form to feature their return, so he gave Gerrold the go-ahead to write them into "The Trouble with Tribbles". ("The Trouble with Tribbles" Starfleet Access, TOS Season 2 Blu-ray) Coon approved of this course of action in agreement with Gerrold's belief that the Klingons were a good fit for the story. Gerrold commented, "This would fit in nicely with his overall plans for the series." (The Trouble with Tribbles, p. 81) Concluded Gerrold, "So, the tribble episode was where we made the decision to have the Klingons be the continuing nemesis for the Enterprise." ("The Trouble with Tribbles" audio commentary, TOS Season 2 Blu-ray)
Klingon Psychology was one of several topics which David Gerrold thereafter found himself having to hurriedly research before writing the episode's teleplay. Even so, while scripting the installment, Gerrold temporarily had some slight difficulty with making the Klingons as nasty as Gene Coon wanted them to be. Coon thoroughly approved of another element of the episode's Klingons, though, Gerrold later recalling, "Gene Coon thought the names I used for the Klingons were deliciously evil-sounding." (The Trouble with Tribbles, pp. 121, 135 & 186)
Regarding the fact that the episode "The Trouble with Tribbles" concludes with many tribbles having been beamed aboard a Klingon ship, David Gerrold supposed about the Klingons, "I'll bet that they didn't let any thoughts of inhumanity trouble them....." (The Trouble with Tribbles, p. 116) When William Campbell was questioned about what the Klingons did with all the tribbles, he responded, "We ate them." (Cinefantastique, Vol. 27, No. 11/12, p. 98) Dave Rossi imagined that the Klingons were "shoveling these things into the engines" at the end of the episode. ("The Trouble with Tribbles" Starfleet Access, TOS Season 2 Blu-ray)
D.C. Fontana was highly approving of several of the actors who played Klingons, enthusing, "We had some really good ones."  Klingon-playing performers John Colicos and William Campbell, who featured as Kor and Koloth in "Errand of Mercy" and "The Trouble with Tribbles" respectively, were veteran television actors. (Star Trek: Communicator issue 114, p. 23)
William Campbell approved of how the Klingons are portrayed in "The Trouble with Tribbles", with the character of Korax being what Campbell perceived as "the nasty one," as opposed to his own character of Koloth. Said Campbell, "I thought that was a good idea; it gave them depth." (The World of Star Trek, 1994 UK ed., p. 121)
Although no Klingons ultimately made any more than one appearance in the original series, Gene Roddenberry believed the series could benefit from a regular Klingon character, a counterpart of Kirk's with whom he would frequently clash. As such, both John Colicos and William Campbell were intended to return as their respective characters of Kor and Koloth. Campbell played Koloth in the knowledge that he might subsequently be hired for as many as thirteen episodes per season. Though Colicos was asked to reprise his role as Kor in both "The Trouble with Tribbles" and "Day of the Dove" whereas Campbell was invited for the first of what was meant to be his multiple reappearances as Koloth, other commitments kept both actors from returning. (The World of Star Trek, 1994 UK ed., pp. 120 & 121; Cinefantastique, Vol. 27, No. 11/12, p. 61; "The Trouble with Tribbles" Starfleet Access, TOS Season 2 Blu-ray)
The Klingons' appearance changed within the original Star Trek series; although dark makeup and heavy eyebrows were the norm, the Klingons of "The Trouble with Tribbles" were much lighter-skinned and more Human-like in appearance. Regarding this change, William Campbell remarked, "[Kang actor] Mike Ansara had a certain gypsy look to him, and John Colicos actually used the name Genghis when describing his character and the kind of make-up. My character in 'The Trouble with Tribbles' was just a guy with a widow's peak and a beard, so basically, we looked like they [the actors playing Humans] looked." (Star Trek Monthly issue 11, p. 53) Explained Robert Justman, "The second time [the Klingons appeared], something went wrong. I didn't see them in their makeup before they were photographed, as I usually did. The first time I saw the Klingons revisited, I was horrified. They were much paler and didn't match what we'd done before. I blew a gasket, but in television, unless it's a total disaster, you can't afford to reshoot. The third outing, we went back to them being darker." (Star Trek: Communicator issue 114, p. 24)
Comic book writer Scott Tipton, who co-wrote the mini-series Klingons: Blood Will Tell, characterized the Klingons in "The Trouble with Tribbles" as generally "very different" from those in "Errand of Mercy". He noticed that they are not only less like Mongol warriors by having less of a swarthy appearance but also by being slightly not as fierce, allowing them to be shown aboard Deep Space Station K-7. "These are kind of more like suburban Klingons," he said. "You know, they're a little laid back, you know, it's like they've been working in an office, they just wanna come in, you know, get some R&R, maybe use a snack room [....] It's enough of a keystone back to what we've seen before that it still feels familiar but it works well because you couldn't put the 'Errand of Mercy' Klingons in this episode, 'cause you wouldn't let those guys onto your space station so they can come have a drink at the bar! So, by the nature of the story, you have to kind of make them a little more refined." ("The Trouble with Tribbles" Starfleet Access, TOS Season 2 Blu-ray)
Another changing element was the depiction of Klingon females. A line by Koloth in "The Trouble with Tribbles" was meant to suggest that females ("non-essentials," as Koloth puts it) don't serve on Klingon vessels. (The Trouble with Tribbles, p. 187) In "Day of the Dove", however, two women are shown as crew members from Kang's battle cruiser. "Day of the Dove" marks the only appearance of any female Klingons in the original series. It was Fred Phillips who created the female variant of the Klingon makeup. (The Star Trek Compendium, p. 119)
The portrayals of Klingons in TOS are largely consistent with one another, though new attitudes were attributed to them in later years. Whereas TOS Klingons were played with what Robert Justman once termed bravura, no one thought of them as honorable warriors yet. "When you got right down to it," said Justman, "they were worthy adversaries and they were killers. They were 100 per cent bad, evil, motivated by the need to be evil. They were thrilled to be evil." (Star Trek: Communicator issue 114, p. 24) Mike Sussman pointed out, "They really seemed much more interested in glory and treachery than honor in those days. Maybe they found the whole 'honor' thing wasn't working for them." (Star Trek: Communicator issue 139, p. 47) Richard Arnold concluded, "In TOS, the Klingons were not very bright bad guys." (Star Trek: Communicator issue 114, p. 27) Ronald D. Moore noted about Klingon culture, "The original series had very, very little in it." ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray)
While working on Remastered TOS, neither Dave Rossi nor Michael and Denise Okuda were ever tempted to add computer-generated wrinkles to the Klingon foreheads, matching the look of the species in later appearances. "Although, I gotta tell ya, the three of us talked about it for a while," recalled Mike Okuda, "and we thought, 'We should propose digitally retouching the foreheads just so we could see [Visual Effects Supervisor] Niel Wray's head explode,' because once he figured out the amount of time it would take to retouch every single frame with every single scene with every single Klingon, they'd still be working today." ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray)
During development of the unrealized TV series Star Trek: Phase II, John Meredyth Lucas wrote a two-part episode entitled "Kitumba" which, if filmed, would have established a radically different Klingon culture to the one developed in subsequent series and films. For a start, it would have been revealed only members of the Empire's warrior caste are called Klingons. The other castes are called the technos, who are the scientists and technicians, and the subjects. The homeworld was referred to as Ultar. A relationship similar to the Emperor and Chancellor in later series would also be established, with the ceremonial Kitumba residing on the Sacred Planet that orbits closer to the sun, while the Warlord presides over political and military decisions on Ultar. (Star Trek: Phase II - The Making of the Lost Series)
Beginning with Star Trek: The Motion Picture, improved makeup techniques and bigger budgets led to the Klingon makeup design becoming more elaborate than it had been in TOS. Faced with the prospect of having much more finances to work with for the Klingons in The Motion Picture, Fred Phillips initially asked Gene Roddenberry if he could do some very alien-looking Klingons, a request Roddenberry approved. (Star Trek: Communicator issue 104, p. 12) In fact, not only did more finances assist with the creation of a cinematic version of the Klingons for The Motion Picture but so did more time. Both elements enabled Phillips to give "character" to the Klingon faces. (Star Trek: The Original Series Sketchbook, p. 209)
Costume Designer Robert Fletcher was instrumental in giving the Klingons a new "look" for The Motion Picture. Maggie Schpak noted, "We had a lot of time [...] so Bob just designed and designed and designed those Klingons." ("Klingon and Vulcan Costumes", Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
The new makeup design included the original complexion and facial hair of the TOS Klingons but also added a bony head crest. (Star Trek Magazine issue 172, p. 59) The inspiration for the post-TOS Klingon makeup came from Planet Earth, an unsold 1974 Gene Roddenberry pilot which starred Diana Muldaur and Ted Cassidy. (Cinefantastique, Vol. 37, No. 2, p. 40) That pilot featured a Klingon-inspired, warlike race of mutant Humans called the Kreeg who had ridges down the center of their foreheads. Robert Fletcher was largely responsible for the addition of the Klingon cranial ridges. "I did sketches for the Klingon, including the knobby forehead and head. The makeup department, very generously, said, 'That's great, we'd like to use it.' Gene Roddenberry was not too enthusiastic. He thought they should look more like just people. I said, 'Yes, but these are real aliens, and they're evil aliens.' I think the people, the audience, wants to see something that is not just folks, that goes beyond just folks." ("Klingon and Vulcan Costumes", Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
It was Gene Roddenberry's idea that the newly added head ridges were actually an outgrowth of the Klingon spinal cord, proceeding up the back of the neck and over the head. (Star Trek Magazine issue 172, pp. 59-60) Robert Fletcher was of a similar opinion. "In my mind, all the bumps on the forehead and so forth are vestigial remains of a people that evolved like crustaceans, like lobsters, who have their skeleton on the outside of their bodies," Fletcher explained. "And over the millions of years, they've lost that complete outside skeleton, but now retain only vestiges of it." ("Klingon and Vulcan Costumes", Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray)) In production notes that Fletcher wrote about the movie's various aliens, he specified about the Klingons, "Spine comes up over head and down forehead (different from series). Hair on side of head as though trying to cover spine." (The Making of Star Trek: The Motion Picture, p. 133) Fletcher also believed that the evolutionary roots of the Klingons were symbolized by an ornamental spine piece that runs down the back of 23rd century Klingon uniforms, such as those designed for and shown in The Motion Picture. ("Klingon and Vulcan Costumes", Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
Once thought up, the Klingon head ridges required considerable experimentation. "Fred Phillips did a makeup test by putting a bald cap on the actor and sculpting the entire thing out of mortician's wax so he would have a crude version of what it looked like in three dimensions," Rick Stratton explained. However, Director Robert Wise – thinking the test makeup was slightly too extreme – was inspired by noticing the knuckles of one of his hands in moonlight. "He had the idea for a more subtle bone structure than the big gnarly spinal cord thing," continued Stratton, "but we thought to ourselves, 'Oh, knuckleheads!' So we did a makeup test with the subtle 'knuckles,' but it wasn't extreme enough. So, we went back to the more vertebrae-like look." (Star Trek Magazine issue 172, p. 60) Stratton also noted of the final design, "It might have looked like a lobster tail." (Star Trek Magazine issue 172, pp. 59-60)
The makeup for the Klingons in The Motion Picture primarily featured a head piece that came down over the brows and back over the head. "It was made in two segments, and they were joined together with cement," reported Mark Lenard. One of these parts was a nose piece that extended down from the upper area of the head piece, over the actor's nose "So that was pretty warm," said Lenard of the entire head piece. "The rest of the makeup was lots of hair and a beard. There is a lot of hair on the sides of the Klingon appliances." (Starlog #42, p. 24)
The creation of the prosthetics meant the makeup team had to take molds of the actors' faces. (Starlog #42, p. 26) The Klingon appliances were sculpted by Rick Stratton along with Mark Seigel and Mike LaValley. (Star Trek: The Original Series Sketchbook, p. 209) Commented Mark Lenard, "The fellows who did the mask, helpers of Fred Phillips, weren't my idea of professionals. They kind of left you alone. And they took a long time putting it on." (Starlog #42, p. 24)
While helping to sculpt the prosthetics, Rick Stratton suggested adding teeth. "When we began running out of stuff to do," he admitted, "I wanted to get an extra day's pay, so I said, 'How about if we make some messed-up teeth for these guys?' It would save time staining their teeth and make them look like they had been chewing on bones or something, but it was all because I wanted another day's pay!" (Star Trek Magazine issue 172, p. 60) The dental appliances remained as part of The Motion Picture's Klingon makeup. (Star Trek: The Original Series Sketchbook, p. 209)
Ve Neill arranged the Klingon makeups for usage, actually applying the makeup for The Motion Picture's main Klingons, of which there were three. (Star Trek Magazine issue 172, p. 60) This required the actors to spend several hours each day just being made up for their Klingon roles. Mark Lenard calculated that this duration was between one-and-a-half to three hours, a time span which varied to enable the makeup artists to redo the makeup in time for the beginning of the day's shoot. (Starlog #42, p. 24) "I put all the heads together, dressed the hairpieces, and glued all the hair on the heads [....] Fred [Phillips] hired some old cronies to do the rest of them, and they came in and brushed out all the hairpieces!" Neill remembered. "All they had to do was put on the heads with the hairpieces on them, and take a rat-tail comb and blend the hairpieces onto the heads, but they brushed them all out, and totally messed up all of the makeups. Every one of those actors came to me and said, 'Hey, you've got to fix my makeup!' and I had to say, 'Oh, no, I'm not going to fix anything!' I don't want any of those old guys mad at me!" (Star Trek Magazine issue 172, p. 60)
Gene Roddenberry tried to explain the differences between The Motion Picture's Klingons and the original ones by saying that the original show had simply never had the budget and makeup technology to envision the species as it should have been seen, so the apparently new Klingons were just Klingons as they were always intended to have been. (Cinefantastique, Vol. 37, No. 2, p. 40) He specifically said, "Just as there are different races of humans, there are different races of Klingons, and the Klingons seen in Star Trek: The Motion Picture are not the same race as the ones we saw on the original series." Since Fred Phillips expected that the fans would wonder about how the Klingons could possibly have head ridges newly added to their faces, he and Roddenberry came up with the explanation of there being a variety of Klingon races, even before the release of The Motion Picture. Despite this, the transformation continued to be regarded as a mystery for decades to come. (Star Trek: Communicator issue 145, pp. 71-72) Roddenberry also stipulated that the Klingons would preemptively attack any foreign entity discovered within Klingon space, such as they do to V'Ger in The Motion Picture. (audio commentary, Star Trek: The Motion Picture (The Director's Edition))
Mark Lenard admitted that, before playing the Klingon Captain in The Motion Picture, he had never imagined playing a Klingon and said this was "because they are the arch enemies of the galaxy." (Starlog #42, p. 24) The actor had trouble with the film's Klingon prosthetics, though, complaining, "This Klingon makeup was very uncomfortable and painful." (Starlog #117, p. 48) He clarified, "[It] was so full of hair, and it was so hot–and it itched." (Starlog #138, p. 35) Despite the discomfort, Lenard found that the makeup was sufficiently movable for the required performances, remarking, "Oh yeah, you could be expressive – even as a Klingon." (Starlog #42, p. 26) Richard Arnold once noted that, despite appearing in only a few brief scenes, Lenard was instrumental in developing a key aspect of the Klingon character. Arnold specified that, by making the Klingon Captain "sympathetic," Lenard changed the Klingons "into having more honor." (Star Trek: Communicator issue 114, p. 27)
The Klingon style for all subsequent Star Trek productions was influenced by the design of the Klingon bridge in The Motion Picture. (The Art of Star Trek, p. 171)
Gene Roddenberry planned for the second Star Trek film to focus on the Klingons, including an exploration of their culture and the motives regarding their passion for battle. (The Making of Star Trek: The Motion Picture, p. 215) However, this did not come to be.
Although Harve Bennett originally planned for the Romulans to be the primary villains in Star Trek III: The Search for Spock, the Klingons were instead made the film's adversaries at the recommendation of Leonard Nimoy, as he convinced Bennett that the Klingons were Star Trek's main antagonists. (Star Trek: The Magazine Volume 3, Issue 8, p. 30) "I've always been more intrigued by the Klingons," Nimoy conceded, "so I suggested the switch, which Harve readily embraced [....] It was Bill Shatner who reminded me that Gene Coon [...] gave us the gift of Klingons." (I Am Spock, hardback ed., p. 223) Nimoy also perceived that the addition of the Klingons was made out of considerations regarding the Genesis Device, which had been established in Star Trek II: The Wrath of Khan. "They would have heard about it and would have been threatened by it. It had overtones of a Soviet-US kind of combat." (Captain's Log, Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray)) Bennett himself added, "That gave us the perfect foil [....] And, of course, Leonard had a marvelous insight into what they should look like. His knowledge of how we could do it made the Klingons the perfect fit; we had our Nazis." (Star Trek: The Magazine Volume 3, Issue 8, p. 30) Bennett also related, "It was only as I was writing it that I realized the Klingons were as dastardly a group of heavies, and that I had made them so. I'd resurrected them from the series, where they were ill-defined or non-defined." He revealed, too, that his decision to replace the Romulans with the Klingons as the movie's villains was because, after viewing all the episodes of TOS, he perceived a "sense of determination and absolutism" in the Klingon episodes that he felt wasn't so evident with the Romulans. (Star Trek III: The Search for Spock audio commentary, Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray)) One unrealized plot thread from the movie, conceived and briefly considered thereafter, was that the Klingons had stolen a Bird-of-Prey from the Romulans (accounting for the reused name). "We agreed that the Klingons would steal the best from anybody," Bennett recalled, "though we didn't have time to show it in the story." (Star Trek: The Magazine Volume 3, Issue 8, p. 30)
In Star Trek III, Leonard Nimoy wanted to thoroughly explore the Klingon mindset. "My thrust always was, 'Let's learn something,' and I think that's the best of Star Trek, always. 'Let's get under the skin of these characters, under the skin of their story, under the skin of their society. Why are they so paranoid [...] angry and hostile?'" (Star Trek III: The Search for Spock audio commentary, Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
Leonard Nimoy believed that having the relationship between Klingons Valkris and Kruge established near the start of Star Trek III was "very interesting and helpful in establishing the context in which the story was going to take place." Nimoy was additionally of the opinion that the audience was taught about an aspect of the Klingon mentality via the on-screen interactions between the two Klingons, particularly that Kruge is willing to sacrifice his beloved Valkris, by killing her himself, simply because she has learned all about the secretive Genesis Device. (Star Trek III: The Search for Spock audio commentary, Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
Klingon aesthetics played into the designing of the Bird-of-Prey, such as Leonard Nimoy giving Art Director Nilo Rodis an idea of what a Bird-of-Prey even meant by showing him an image of a Klingon. "I looked at that and I thought, 'OK, I think I understand,'" Rodis remembered. Particular aspects that he took inspiration from, in designing the Bird-of-Prey, were the Klingons' color scheme and that they apparently like decoration. "If you look at the Klingons, there is something fairly gothic and art deco about them," Rodis pointed out. "If you notice, they never wear simple, undecorated costumes; it's all kind of metallic and leather, with piping and stuff [....] Also, even though the Klingons aren't green, they are definitely not blue. They lean more toward gray/green." (Star Trek: The Magazine Volume 3, Issue 8, p. 58)
The Klingons were storyboarded to appear, in Star Trek III, much as they had been seen in The Motion Picture. ("The Klingons Attack" and other storyboard sequences, Star Trek III: The Search for Spock (Special Edition) DVD special features) Specifically at the request of Leonard Nimoy, though, Robert Fletcher was made responsible for duties encompassing Star Trek III's redesign of Fred Phillips' redesign of the Klingons. Fletcher collaborated with Tom Burman of the Burman Studio, who fabricated Fletcher's designs; they thus created the third-generation version of Klingons, whose bony foreheads were less pronounced than those shown in The Motion Picture. (The Art of Star Trek, p. 226) "We tried to make them somewhat less brutal, less prominent," stated Fletcher, "so that you get a better sense of the Klingons' individual faces." Burman shared Fletcher's conclusion that the Klingon forehead had to be revised. "It was just too cartoonish, and I didn't want a Star Wars look in this movie," Burman related. "There had never been a good marriage between the forehead appliance and the actors' faces. We tried to keep them in character rather than have these obtrusive things on their heads." Burman believed that doing each of the Klingons right took two hours. (The Making of the Trek Films, UK 3rd ed., p. 52) The makeup process began with the application of a bald cap and forehead appliance. Still included as part of the makeup was faux facial hair. (Cinefantastique, Vol. 17, No. 3/4, p. 83)
Director of Photography Charles Correll was tasked with using lighting to ensure the Klingon makeup in Star Trek III looked believable throughout the movie, so that any naturally occurring anomalies in the makeup were not highlighted. Given that the bridge set for the film's Klingon Bird-of-Prey was top-lit and deliberately kept dark, Correll said about the Klingons being shown on their own ship, "We were lucky [...] and I think we accomplished what we had to do." The dim lighting not only helped make the Klingon prosthetics less pronounced but also added to how dramatic the Klingons appeared, which the framing of the shots also aided. "Shooting these guys on the Klingon bridge was all about getting in tight, getting mysterious, getting intense," commented Leonard Nimoy. "Very tight, very up-close, intense stuff, to emphasize the power of them, the presence of them, the danger of them, and their conspiratorial attitude, their whispering and the tension that grew out of that." (Star Trek III: The Search for Spock audio commentary, Star Trek III: The Search for Spock (Special Edition DVD/Blu-ray))
The Star Trek III portrayal of Klingons took inspiration from Japanese history. "Harve [Bennett] had the notion that the Klingons were like Samurai warriors," explained linguist Marc Okrand. (Star Trek: Communicator issue 114, p. 27) Robert Fletcher agreed with Bennett, later saying of the Klingons, "I always liked to think of them as authoritarian, almost feudal, like Japan had been." (The Making of the Trek Films, UK 3rd ed., p. 52) As such, both the Klingon costumes and Klingonese language in Star Trek III were influenced by the feudal Japanese culture. (The Art of Star Trek, p. 226; Star Trek: Communicator issue 114, p. 27; The Making of the Trek Films, UK 3rd ed., p. 52)
At one point, Leonard Nimoy remarked that, on Star Trek III, he was "happier than ever to be working with Klingons!" and that this was due to Kruge actor Christopher Lloyd's portrayal in the film. (I Am Spock, hardcover ed., p. 226) For his part, Lloyd once expressed that he thought the Klingon makeup was helpful to performances, commenting, "That kind of makeup, when it’s put on well, it enhances what you’re doing and gives you more confidence that you’re going to be able to portray the character and make it believable." 
Leonard Nimoy selected a single forehead design to be used for all the Klingons in Star Trek IV: The Voyage Home. (The Art of Star Trek, p. 254) John Schuck, who portrayed the Klingon ambassador in both that film and Star Trek VI: The Undiscovered Country, thought the Klingons had begun to undergo a gradual transformation of ultimately becoming a tad friendlier by the time of Star Trek IV. After discussing this subject with Gene Roddenberry, Schuck recalled, "It seemed to me that in the minds of the creators, the Klingons had matured [....] I asked him about it. He said it was time for the Klingons to take on a dimension which showed that the culture had changed. Alliances change. There can be progress." (Star Trek: Communicator issue 114, p. 28)
Much of the focus on the Klingons in the Star Trek films preceding the advent of Star Trek: The Next Generation was not on their culture. Ronald D. Moore perceived, "The movies were sort of more about art direction, sort of how they behaved, and sort of changing their makeup than about anything cultural." ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray)
On Star Trek: The Next Generation, Gene Roddenberry was originally averse to Klingons appearing at all. This was because they were one of several original-series aliens (also including Vulcans and Romulans) which Roddenberry wanted to avoid returning until the new series had been accepted for its own merits. (Star Trek: The Next Generation Companion, p. 6) Hence, the plan was for the Klingons not to reappear in the new series. (Star Trek Monthly issue 10, p. 50)
Robert Justman began an 18 October 1986 memo to Gene Roddenberry, concerning the show's bible, with the sentence, "Despite your aversion to using Klingons in the new series, I think I've thought of something which might just change your mind." Justman went on to propose a resident Klingon serving aboard the Enterprise, suggesting that the military skills and prowess of the Klingon species might cause such a person to be well-suited for a role in the ship's crew. (Star Trek: The Next Generation - The Continuing Mission, p. 15) Later, Justman elucidated, "I thought that having a Klingon as part of Starfleet would signify something very important. And when Gene told me that he didn't want the Klingon in the show at all, I remonstrated with him, and said, 'Just imagine what it means. It means that we can grow as a race and that things change.' Gene suddenly realized that what I was proposing fit right in with his optimistic view of the future." (Star Trek: Communicator issue 115, pp. 73-74) Okaying the character concept that then became Worf, Roddenberry finally agreed that a Klingon alliance with the Federation might be indicated via the addition of the Klingon Starfleet officer, limiting the focus on the warlike nature of the species. (Star Trek: Communicator issue 139, p. 70) Whoopi Goldberg once cited the fact that "the Klingons have cooled out" as an indication that "things are going well for the world." ("Mission Overview", TNG Season 2 DVD/Blu-ray special features) However, the adoption of Plan B actually involved retaining not only the Klingon species itself but also their fierce image of "guys you've got to watch out for," meanwhile having them join the Federation. (Star Trek Monthly issue 10, p. 50)
In the first writer's/director's guide for TNG, Gene Roddenberry stipulated that "no stories about warfare with Klingons" should be submitted. However, he and the rest of the staff soon realized that TNG had quickly established a style of its own, so they allowed Worf's Klingon background to be explored. (The Art of Star Trek, p. 92)
African-American actors were often cast as Klingons in TNG and subsequent Star Trek productions. Worf actor Michael Dorn believed this practice wasn't "about race" and was instead carried out because it lessened makeup time, as the performers already had a brown complexion without having to have their skin painted that color. (Stardate Revisited: The Origin of Star Trek: TNG, Part 2: Launch, TNG Season 1 Blu-ray)
The Klingon makeup schemes for TNG were influenced by previous Klingon facial appearances. "I already had the basic design from the motion pictures," Michael Westmore observed. (Star Trek: Aliens & Artifacts, p. 59) The Klingon makeup for The Next Generation was thereafter specifically based on the Klingon look Fred Phillips had developed for The Motion Picture. (The Art of Star Trek, p. 92) Westmore, however, opted to depart from what had gone before, later claiming that the "subtlety of the original ridges did not translate onto television." (Star Trek 30 Years, p. 57) He noted, "It's one area where I had a lot of license with it, because I was given photographs of former Klingons and there were no two alike. They were all different. So, I was given the opportunity to go ahead and create a new Klingon look that hadn't been done yet." ("The Making of a Legend", TNG Season 1 DVD & Blu-ray special feature) Westmore took the decision to deviate from the features of past Klingons upon first thinking about the species for The Next Generation. "Up until then, the Klingons were brown and had a bony ridge running down their foreheads. I felt, for such a fierce warrior race, just putting foreheads on them wasn't enough, so I asked Gene Roddenberry and Rick Berman to let me try something different." (Star Trek Magazine issue 172, p. 61)
Michael Westmore then changed the Klingon facial design in numerous ways. He stated, "I added a Shakespearean style of facial hair and a forehead bone structure based on dinosaur vertebrae and I was able to modify motion picture Klingons for television." (Star Trek: Aliens & Artifacts, p. 59) He also said, "I suggested bringing their makeup down into their face by using noses and teeth, rather than having just a forehead." (Star Trek: The Magazine Volume 2, Issue 12, p. 25) A unique set of teeth was cast for each speaking actor who was to play a Klingon on TNG. Similarly, an early policy was devised by Westmore whereby each Klingon forehead was cast with a different ridge pattern. Westmore soon came to regret this policy, however. (Star Trek: The Next Generation Companion 3rd ed., p. 21) Especially due to the series featuring Worf as a regular character, the Klingon makeup scheme for TNG continued to become more refined throughout the series. (The Art of Star Trek, p. 92) Stated Michael Dorn, "I feel I've been a model for all Klingons." (Star Trek: Communicator issue 104, p. 60)
Early Klingon forehead prosthetics caused some skin problems. Michael Dorn said, "The glue was the number one thing I had a major problem with." This was remedied, after Dorn complained about it to the producers, in the second season of TNG. (Star Trek Magazine issue 172, p. 63) Korris actor Vaughn Armstrong's Klingon forehead prosthetic in the episode "Heart of Glory" likewise caused him to develop a rash by the time it was first removed, as he had an allergic reaction to the makeup. "They were very concerned," Armstrong related, "because they knew they were going to use it a lot, but they fixed it and it never happened again." (Star Trek: The Magazine Volume 2, Issue 9, p. 43)
While Michael Dorn was preparing to play Worf, Gene Roddenberry wanted previous Klingons to have minimal influence on the forthcoming portrayal, advising Dorn, "Forget everything you've ever read or heard about Klingons." (The Official Star Trek: The Next Generation Magazine, Vol. 15, p. 46)
It was "Heart of Glory" which introduced The Next Generation Klingons (except for Worf's previous appearances and an illusory Klingon temptress in "Hide and Q"). Ronald D. Moore once referred to "Heart of Glory" as a notable episode for developing the Klingons. ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray) In agreement, Michael Dorn said, "For my money, that was the first real Klingon episode of that first season [....] I think that episode worked because it showed Klingons could be eloquent beings. We gave audiences something where they could ask, 'Wait a minute! Who are these people?'" (Star Trek Generations - Official Movie Souvenir Magazine) Dorn was also of the opinion that the outing not only inspired questions regarding the Klingons but also answered some. Dorn remarked, "I consider 'Heart of Glory' to be an information episode because it gave you everything you wanted to know about what happened with the Klingons. Why did they become allies? [....] That type of thing." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 165) The episode set a precedent for Klingon mythology that was later to be followed in many other installments. "And I think this is something that they probably didn't realize," Dorn said of the TNG producers and writing staff, "when they started down this road of Klingon stuff, that they were gonna have this mythology." ("Making It So: Continuing Star Trek: The Next Generation, Part 1: Strange New Worlds", TNG Season 2 Blu-ray)
Maurice Hurley, who co-wrote the story and scripted the teleplay for "Heart of Glory", observed that the Klingons helped bring a sense of balance to the series. "With the Klingons you're dealing with emotion and passion. You've got somebody who can say something. You need that balance in the show sometimes," he opined. "The show gets so intellectually smug and self-serving, and you need something like that to break it off; someone willing to storm the barricades." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 182) Additionally, Hurley expressed that "Heart of Glory" presented the Klingons in such a way as to be highly relatable, saying, "The hunter remains within us all. That need to stalk and kill, drink warm blood and howl at the moon is part of who we are." (Star Trek: The Magazine Volume 2, Issue 12, p. 53) This approach helped the Klingon-playing actors to find their characters' mindsets. "You always start from the human element of these people," stated Vaughn Armstrong. "You find out what it is about them that you can relate to, and then you add other little characteristics as you go along and see the makeup, talk to the director, and all of that." (Star Trek: The Magazine Volume 2, Issue 9, p. 43)
Director Rob Bowman was extremely familiar with the Klingons before directing "Heart of Glory", later saying, "I knew the Klingons very, very well from the movies and the original series." (Star Trek: The Magazine Volume 2, Issue 12, p. 21) Vaughn Armstrong noted about Bowman, "He also said, 'We want the Klingons to be the bikers of the universe!'" (Star Trek: The Magazine Volume 2, Issue 9, p. 42) In "Heart of Glory", Bowman introduced the idea that it took three phaser hits to down a Klingon, with killing blows. "I wanted to make these guys as tough and as bad as I could," he said. ("Rob Bowman – Director of a Dozen", The Official Star Trek: The Next Generation Magazine Vol. 10)
The Klingon alliance with the Federation was at first meant to feature in the story which became "Conspiracy". In the episode's original form, fears that the peace with the Klingons had made the Federation complacent motivated a Starfleet conspiracy that was based solely on paranoia. The notion of the concern over the alliance was omitted because Gene Roddenberry rejected this early version of the installment. (Captains' Logs: The Unauthorized Complete Trek Voyages, pp. 168-169)
Rob Bowman thought the Klingon action in "A Matter Of Honor" made it a fun episode to direct; after doing so, he remarked, "I guess there's a spirit inherent in the Klingons that seems to push it forth in a certain direction with the characters and the camera." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 176)
In "A Matter Of Honor", the Klingons were intended to be used to shed some light on a common social problem prevalent at the time of the episode's making. This was, namely, what it was like to be the only person of either white or black skin coloration while surrounded by people of the other color. The Klingons were selected to illustrate this theme as a spin on the usual arrangement of a predominantly Human crew serving aboard the Enterprise-D alongside Worf. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 176)
Producer Burton Armus not only co-wrote the story and wrote the teleplay for the Klingon-centric episode "A Matter Of Honor" but was also interested in an ultimately undeveloped Klingon story that was written and pitched for the series by freelance writer Marc Scott Zicree. This never-produced episode would have established why the Klingons looked differently in the new series and films to how they had appeared in TOS. Though Armus wanted to buy the story concept, he had left the series before he could. (Star Trek Magazine issue 172, p. 60)
As co-writer of the story for Star Trek V: The Final Frontier and the director of that film, William Shatner observed that the Klingons provided an important structural function to the film's writers. "The Klingons were always regarded as an added threat," he stated. "We kept them alive throughout the story–almost mathematically mapped it out–so that the element of tension would be there. Otherwise, it would become, 'Are they going to see God, or aren't they–yes or no, yes or no,' like Ping-Pong balls. This way the elements of the unknown were kept alive, adding more tension and interest to the story. And, of course, they became an interesting way to resolve the final problem of how to get Kirk back on the ship." Harve Bennett cited the Klingons' rescue of Kirk from Sha Ka Ree as contributing to the surprises throughout the movie, saying the reveal of the Klingons as Kirk's rescuers was meant as a "big surprise." (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, pp. 51 & 50)
William Shatner was pleased with the casting of Todd Bryant and Spice Williams in the Klingon roles of Klaa and Vixis respectively, commenting, "They were physically right for the Klingons and were obviously talented enough to do the roles justice." These two actors spent a great deal of time preparing to play their roles. For instance, both performers had to endure a three-hour makeup session each morning to look sufficiently Klingon. (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, pp. 78 & 147-148)
For each of the performers cast to portray a Klingon in Star Trek V, the application process began with a bald cap being positioned over the performer's hair, after which one of the Klingon forehead appliances was added. (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, p. 148) William Shatner permitted Richard Snell to produce each of the film's Klingon foreheads as a distinctive design. "That opened the door and now the sky's the limit," noted Snell. (The Art of Star Trek, p. 254) The forehead prosthetic was attached to the actor's skin using a strong adhesive glue. Both the newly added appliance and the skin were then painted with makeup, which was a mixture of acrylic and adhesive. Each performer then donned a hairpiece, helping complete the illusion. (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, p. 148) The only Klingon which Makeup Effects Artist Kenny Myers created for Star Trek V was the Klingon god. (The Making of the Trek Films, UK 3rd ed., p. 90)
Given the extreme degree of preparation involved, William Shatner was very excited to film the Klingons. He was not disappointed, thrilled with the performances of Spice Williams and Todd Bryant. (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, pp. 147 & 148)
At one stage, Ron Moore cited "The Emissary" as a significant installment for developing the Klingons. ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray) In crafting the plot of "The Emissary", the writing staff of TNG toyed with the concept of the Klingons having allied themselves with the Federation without actually having become members of the Federation. "That gave us something to play with," noted Melinda M. Snodgrass, who was serving as a story editor on the series at the time the episode was written and produced. (Cinefantastique, Vol. 21, No. 2, p. 45)
At the time Ron Moore wrote his first produced episode for TNG, "The Bonding", he had become interested in the Klingons and had read about the species in the novel The Final Reflection, a book which had shaped much of his thinking about Klingons. ("The Bonding" and "Sins of the Father" audio commentaries, TNG Season 3 Blu-ray) Indeed, he had also begun considering several aspects of Klingon culture, concepts which he explored in "The Bonding". These ideas included Klingon honor, Houses and bonding people to them. However, Moore was unaware he was about to become synonymous with Klingon episodes. "I certainly didn't anticipate [...] that I would keep embellishing," Moore admitted, with a laugh, "on this culture, over and over again, throughout my Star Trek tenure." ("The Bonding" audio commentary, TNG Season 3 Blu-ray)
Klingons were present in an initial plot thread developed for but dropped from the episode "Deja Q". "We developed a whole story about how we were going to come into a war with the Klingons," detailed Michael Piller. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 191)
A poetic line of dialogue concerning the Klingons (and explaining why Worf never gazed at the stars while in Ten Forward, unlike many of his crewmates) was similarly excised from "Yesterday's Enterprise". Ron Moore, who wrote the line, recalled, "Worf said something about [...] 'To look at the naked stars is to ask them questions, and Klingons do not ask questions for which there will be no answers; we make the stars ask questions of us.'" ("Yesterday's Enterprise" audio commentary, TNG Season 3 Blu-ray)
One of the most definitive episodes for the Klingons is "Sins of the Father". It gave an insight, for the first time, into how Klingons behaved on their homeworld. The story basically came about as a combination of two Klingon-centric scripts, "Our Brother’s Keeper" by Beth Woods and "Brother to Dragons" by Drew Deighan, though Ron Moore also found himself assigned to help develop the episode.
At the outset of Ron Moore working on "Sins of the Father", Michael Piller asked Moore to write him a Klingon-defining memo. This was because – as Piller wasn't a Star Trek fan – he was attempting to understand who the Klingons were. Since Moore was a fan, he had his own opinions about the nature of the Klingons, which he imbued in the memo. The fact that very little had been firmly established about the Klingons, canonically, provided Moore with a lot of creative freedom to invent facets of their culture in the document. Apart from a couple of key installments that previously developed the Klingons in TNG, Moore also recalled the few details about them that had been set up; "Certain things about their culture having, sort of, honor-bound traditions were sort of established." ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray) The experience of having written "The Bonding" was an influence on the memo. ("The Bonding" audio commentary, TNG Season 3 Blu-ray) Much of its content was inspired by literature, with The Final Reflection serving as the primary influence. In general terms involving Houses and conflicts between them, the fictional universe of Dune, created by Frank Herbert, was very influential too.
Entitled "Klingon History and Culture: A Brief Overview" and running two pages long, the memo began with a description of the Klingon Empire, outlining that the planets therein enjoyed "many advantages and benefits of their association with the Klingons." The memo went on to say, "The Klingons are not evil, tyrannical pirates bent only on pillage and plunder. They have a strict, almost unyielding code of ethics and honor and take their responsibilities as rulers seriously." Following a description of the Klingon homeworld, the memo continued by saying, "Klingon society could most closely be compared to that of Sparta or feudal Japan." A description of the Klingon Empire's political system followed, involving the Klingon High Council and establishing that there was an Emperor. The document continued, "Klingons have a very complex and highly developed code of conduct, involving almost every aspect of their lives. Their sense of honor and integrity is integral to their very being." The text then detailed Klingon Houses and the high importance with which Klingons held them, before stating, "Strangers must prove their worthiness before a Klingon will accept them as an equal. Weakness, either mental or physical, is not tolerated. Klingons are born to be warriors. Time spent in other professions is used only to expand their knowledge and range of skills in preparation for being a warrior. Several of the races they have conquered now serve as the merchants, farmers, traders, machinists, et cetera, of the Empire. Klingons respect courage, strength and cunning, in that order [....] Klingons respect the declared war, the killing stroke, the blood feud, death in the field of battle and clear positions of hostility."
After Ron Moore and W. Reed Moran co-wrote a script that was based on the teleplays for "Our Brother’s Keeper" and "Brother to Dragons" and was entitled "Sins of Our Fathers", Michael Piller wrote a criticizing memo in which he stated, "I [...] feel we haven't adequately defined or explored the Klingon culture." Contrastingly, at another point during the writing of the episode, Piller decided the Klingon ceremonies established in the installment were too numerous, excluding one which Moore later described as "an elaborate sort of a take-off on a Japanese tea ceremony that was sort of a traditional greeting when someone came to your home." The ways in which the Klingons ultimately dealt with Worf's brother, Kurn, changed considerably between the drafts, though the Klingons dishonored Worf at the end of all drafts of the amalgamated script, a plot point whose unresolved quality was then very rare for the series and allowed the installment to become the first part in a Klingon arc.
Focusing on Klingon politics to such a degree as "Sins of the Father" does involved an element of risk. Observed Ron Moore, "It's really interesting how deep into Klingon politics the show got. I mean, this was a fairly unheard-of thing [....] And it was asking the audience to buy into that and to actually care about that. And Michael [Piller], I remember, was [...] always kind of on-the-fence about it. There were times when Michael Piller thought that was great, it was taking the show in a new direction. Other times, he kind of went, 'You know what? I don't know if the audience is gonna care about whether the Klingon Empire falls into civil war or not." By continually leaning on how the political goings-on had dramatic repercussions for Worf, Moore thought the other side of the episode was successful. "You are caught up in the political nature of the story," he expressed. ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray)
The developing Klingon mythology was significantly explored in "Reunion". "That was really where we began embroidering the larger saga that was sort of developing about the Klingons and Worf," reflected Ron Moore, "and that would lead to the civil war and 'Redemption'." ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray)
Production staffers such as Doug Drexler tried to help performers playing Klingons – for instance, Gowron actor Robert O'Reilly – with their portrayal. "There were actors who came in to play Klingons who had never seen the show," said Drexler. "So it was part of the job, as the makeup artist is applying their makeup, to help the actor find the proper mindset." (Star Trek: The Next Generation 365, p. 212)
Robert O'Reilly believes that, from The Next Generation episode "Redemption II" onwards, the Klingons developed a sense of humor. "I think the writers started edging towards that," reflected the actor. "They were also scared of it. They didn’t want to go too far. Eventually I think most of the writers went, 'Yeah, we can go there.' From that moment on, I think Klingons could have a sense of humor."  In a 1995 interview, however, O'Reilly stated, "I've noticed that most Klingons don't have a sense of humor and I have always felt that was due to a choice of playing it too much one-way." (Star Trek: Communicator issue 104, p. 54)
Leonard Nimoy wanted to use Star Trek VI: The Undiscovered Country to explore Klingons and their culture. "It seemed to me that this movie presented us with a perfect opportunity" to do so, he said in retrospect. At the time, Nimoy gave much consideration to how the Klingons were similar to the Soviet Union. Influenced by the fall of the Berlin War and the Soviet government clearly beginning to crumble, Nimoy intentionally represented the Klingons as encountering an analogous predicament. The presentment of the Klingons in an alternative draft of the script, however, frustrated Nimoy. "The story never explored the Klingon culture the way I'd hoped it would [....] I was hoping for greater insight into the Klingons." (I Am Spock)
During early development of Star Trek VI, the Klingons were intended to be established as having evolved from a reptilian state. The film, as initially conceived, would also have introduced Klingon tribes, even more primitive and violent than the usual Klingons. These aspects of the plot were discarded because they were thought to be overly expensive. As for the possible ancestry of the Klingons, Gregory Jein – who served as props master on Star Trek V as well as on Star Trek VI – theorized that they developed from an underwater species. "My philosophy is that the Klingons came out of the sea originally," he mused, "and the sea was their basic cultural heritage." Jein took inspiration from this belief when crafting many of the Klingon props from the two films he worked on. (The Making of the Trek Films, UK 3rd ed., pp. 104 & 129)
For Star Trek VI, Richard Snell was made responsible for designing and fabricating the Klingon makeups, enormous numbers of which were needed. Klingon appliances were produced by a staff employed by Snell's makeup lab. "Since the Klingons were to play such a major part in the proceedings," explained Makeup Supervisor Michael J. Mills, "the director wanted them to be as believable as possible. He wanted the audience to watch the actors' faces and not be distracted by the makeups. So every one had to be a custom job – which translated out to be about three-and-a-half hours. Richard Snell did a great job of coming up with all sorts of different designs for the Klingons, and we used the newest techniques and glues and paints for the applications – which was important since these characters were being seen face to face with the principal actors playing humans. The appliances had to be very thin in order to allow the expressions on our actors to come through and read clearly. Ron Pipes, working with Richard Snell, did a lot of work designing the wigs, which played a substantial role in making the characters look more believable. Our hairstylist, Jan Alexander, was instrumental in coming up with various braids and jewelry which suggested a tribal people with a whole heritage and history behind them." (Cinefex, No. 49, pp. 42, 44 & 45)
The Klingons in Star Trek VI were given lavender blood specifically for ratings and plot purposes. (citation needed • edit) In the scenes where free-floating Klingon blood droplets could be seen in zero gravity, however, the blood was colored red, as it has been on television.
As for preparing to portray a Klingon warrior, Richard Herd – who played L'Kor and, at that time, knew people who had played other Klingons – remarked, "There’s a certain way you have to carry yourself. You have to really be able to project the violence and the anger [....] All you have to do is think of the Spartans. They say, 'They’d rather have you come home dead on your shield than come home a coward.'" 
Use of the Klingons in "Rightful Heir" enabled Ron Moore, much to his delight, to write an episode about religion. "That was kind of a forbidden topic, basically, in Gene [Roddenberry]'s universe, but with the Klingons, you could go there," Moore reflected. Using Kahless as an allegory for Jesus Christ, Moore used the installment to speculate about how the Klingons might react to the return of such a figure. "There was something fascinating to me," he admitted, "about the idea about, you know, if you could clone Jesus and brought him back today, how would people treat him and how would it affect their faith, how would it affect politics." ("Sins of the Father" audio commentary, TNG Season 3 Blu-ray)
The Klingons who were to feature in DS9: "Blood Oath" were originally non-specified, aged Klingon acquaintances of Curzon Dax. The storyline, as initially conceived by writer Peter Allan Fields, revolved around them and Jadzia Dax. Writing staffer Robert Hewitt Wolfe, a fan of the original series, then influenced the plot. (Star Trek: Deep Space Nine Companion, p. 131) Fellow writing staffer Ira Steven Behr recollected, "Robert Wolfe and I were talking and he said as a throw away, 'Too bad we can't use any of the old Klingons.' I went to Michael [Piller] and thought we would have a whole discussion on it, but Michael's eyes just lit up and he said, 'Absolutely, see if we can find them.'" (Cinefantastique, No. 25, No. 6/Vol. 26, No. 1, p. 107)
Three actors who guest-starred in leading Klingons roles in the original series were thereafter brought back to play the same members of the species in "Blood Oath", a trio comprising of John Colicos, William Campbell and Michael Ansara as Kor, Koloth and Kang respectively. William Campbell at first expected that the characters would look much as they had done, later reflecting, "When I was asked if I was interested in coming back [...] I thought we would be the 'old' Klingons, who didn't evolve with the carbuncle on the head and the various changes that had been done to them. I even said to my wife, 'We'll be the same as we were, only older.' But when I walked in and said to Rick Berman, 'Somebody said we were going to have to put this makeup on, a la Michael Dorn,' he said, 'Well... yeah!'" (Star Trek Magazine issue 172, p. 61)
The change in the characters' appearances was puzzling for the other performers too. Recounted John Colicos, "I thought, 'How do I put this look together with what he (Kor) was? How did he mutate into this monstrous lizard?'" (Star Trek: Communicator issue 104, p. 19) Michael Ansara remembered, "That was my first question to them [the producers]. Why was Kang all changed now? I tried to understand why the make-up for my Klingon had changed so much, with the putty on the head and all of that." (Star Trek Magazine issue 116, p. 40) William Campbell also asked Rick Berman if there was a reason why the Klingons had changed so much. (Star Trek Magazine issue 172, p. 61)
The producers told the returning actors their new look was part of the Klingon aging process, explaining that Klingons live very long lives. (Star Trek: Aliens & Artifacts, p. 128) "They said 'You have to realize that Klingons live to be a hundred years longer than normal and they change gradually,'" recounted Michael Ansara. "That was the excuse they gave me." (Star Trek: Communicator issue 104, p. 18) Ansara also recollected, "They told me that the Klingons grow those bumps and ridged foreheads as they get older [...] The reason we Klingons had changed so much, with the bumpy heads and whatnot, is that we Klingons live to be 300 years old." (Star Trek Magazine issue 116, p. 40) Recalling Rick Berman's answer for the transformations, William Campbell relayed, "He said, 'Bill, it's about 100 years later [than the original series], and this is the way the Klingons look now, and they've evolved into this.'" (Star Trek Magazine issue 172, p. 61)
Due to the lengthy application process, the performers were disappointed with the restyled Klingon makeup. John Colicos complained, "It was unbelievable getting up at four o'clock in the morning to put on this monstrous makeup [....] This new look took four hours [to put on]." (Star Trek: Communicator issue 104, p. 19) Michael Ansara agreed, "I preferred the original look because it wasn't so heavy with makeup [....] I didn't expect four hours of makeup in the morning and two hours to take it off at night." (Star Trek: Communicator issue 104, p. 18) William Campbell, however, described the makeup job for his character of Koloth as requiring a three-hour application process, also expressing that it was discomforting. (Star Trek Monthly issue 11, p. 54) As well as saying that the addition of the makeup took three hours, he also concurred that it took two hours to take off at night, commenting, "The hours were horrendously long, but we got through it." (Star Trek Magazine issue 172, p. 61) In another interview, Ansara stated it took four hours to remove his makeup late each night, also saying, "Getting in and out of the makeup was difficult, but as an actor, it's part of the business. We know that going into it!" (Star Trek Magazine issue 116, p. 40) By comparison, the duration needed to apply Michael Dorn's makeup as Worf, by the end of Star Trek: The Next Generation's run, was merely an hour. (Star Trek: Communicator issue 104, p. 63)
Robert O'Reilly appreciated "The House of Quark" for establishing additional facets of the Klingon mythos, noting, "It adds to the on-going revelation of Klingon culture. We learn more about the institution of marriage, inheritance and what really constitutes an honorable death. We even hear a bit about Klingon law and see what [an] upper-middle-class Klingon home is like." (Star Trek: Communicator issue 104, p. 54)
Upon securing the role of B'Elanna Torres on Star Trek: Voyager, Roxann Dawson initiated thorough research into the Klingons. "I asked the producers for every pertinent episode which could tell me about Klingons, so I watched very closely and I began to read The Star Trek Encyclopedia. And because I accumulated a virtual library of Klingon lore, I found myself carrying out massive historical research on the race–even though Klingons are obviously futuristic beings." (Star Trek: Communicator issue 104, p. 55)
The reason the Klingons were brought onto Star Trek: Deep Space Nine in its fourth season was that Paramount and the show's producers, attempting to overcome slightly slipping ratings in the third season, were trying to appeal to fans of TNG who were not regularly watching DS9. "The first thought we had was to reintroduce the Klingons," remembered Rick Berman, shortly after the announcement that the species was about to return. "I have always felt that the Klingons were the most accessible bad guys Star Trek has ever had [...] and by taking the Federation/Klingon truce and unraveling it, we were not going to affect the plot lines of the movies or of Voyager, since they are nowhere near an area of space to be affected." Ronald D. Moore agreed, "Everyone wanted to see more of the Klingons as part of the franchise [....] Everyone thought bringing the Klingons back as villains again would energize the series and give it a new direction to go in this year." (Star Trek: Communicator issue 104, pp. 9 & 60)
Robert O'Reilly was aware of DS9 focusing on the Klingons to a great degree. "When I came on to that," he recalled, "it was sort of a nightmare for the show because, for whatever reason, the writers wanted 20 other Klingons with me. So it was a Klingon show, and [....] the Klingons [were] larger than life. It wasn’t so individual; it was like a massive army coming behind me." 
A story Robert O'Reilly tells in an interview in the DS9 Season 7 DVD is that a long running joke among actors who have played Klingons is that they do not want to appear in the films as, he believes, the only purpose of a Klingon in one of the films was to be killed off. He was proven right in Star Trek Generations.
DS9: "Trials and Tribble-ations" made the change in the Klingons' facial appearance part of Star Trek canon. Ron Moore recollected, "Early in the discussions [about that episode], we knew, 'Well, there's these Klingons that don't look like our Klingons. Got to address it; hard to put Worf in a room with them and say they're Klingons and not comment on it, boys and girls!'" Believing that all proposed in-universe explanations for the Klingon makeup change were preposterous and ridiculous, however, the writing staff of Star Trek: Deep Space Nine attempted to deal with it in as minimal a way as possible. "There's no way around this," conceded Moore, "so we just said, 'Just have Worf say it's a long story and leave it at that, you know? And that's fine.' And it's a wink and a nod to the audience, like, 'Okay, we know this doesn't make sense. Just go with us, okay?'" ("Trials and Tribble-ations: Uniting Two Legends", DS9 Season 5 DVD/TOS Season 2 Blu-ray special features) The comment, which was thought up by Ira Steven Behr, thereby discreetly makes light of the fact that the producers and writers of Star Trek had debated for years whether or not to lay this question to rest, once and for all, by incorporating the subject into an episode. Behr explained about the line, “It came out of the story break. It got a huge laugh in the room. We knew we had to deal with the question, but it’s really an annoying, boring question, because the real answer is obviously that makeup has changed over the years, in terms of money and quality. We wanted to shine it on, but not really shine it, and having the line 'We do not talk of it,' come out of Michael Dorn’s mouth seemed to work.” (The Magic of Tribbles: The Making of Trials and Tribble-ations) Due to leaving the question essentially unanswered, while working on DS9, Moore announced, "We have no explanation for the smooth-head/bumpy-head transition and nothing in the show should be taken as addressing that point." (AOL chat, 1998) For recreating some old-style Klingons in "Trials and Tribble-ations", the Klingon-playing actors had to be made up with the same swarthy, shiny brown makeup as used in the original series. (The Magic of Tribbles: The Making of Trials and Tribble-ations)
By the end of DS9's fifth season, the Klingon makeup included approximately thirty-five different ridged forehead designs, representing the various Klingon Houses. Applying the Klingon features took longer than they had required during the making of the original series. "People would be surprised to know the make-up only takes 20 minutes," commented Michael Dorn. "It's the gluing of the hair that takes most of the time. When we can speed that up, I'll be a happy man." On the other hand, the task of wearing the makeup had become progressively easier, including for Dorn as Worf. "The forehead weighs less than an ounce," said Michael Westmore, "but he's only glued around the edges now, which could also mean more touch-ups." (Star Trek 30 Years, p. 57) Similarly, by the time John Colicos reappeared as Kor in "Once More Unto the Breach", the prosthetics were not so impractical as they had been in "Blood Oath". "The make-up took far less time to apply," analyzed Colicos, "and getting it off no longer rotted my skin." (Star Trek Monthly issue 55, p. 38)
To have the Klingons participate in the Dominion War, the writers had to minutely change the Klingons' typical gung-ho attitude. Ronald D. Moore clarified, "The Klingons can't be too suicidal. They're fighting a long and bitter war against a very strong opponent. They do have to husband their strength and their manpower to a certain extent." (AOL chat, 1998)
Some consideration was given, at about the start of Star Trek: Enterprise, as to whether the producers would try to explain the reasoning for there being two different-looking types of Klingon. Shortly before the series began, an uncertain Rick Berman revealed, "We've thought about it [....] I think it is something we have discussed possibly doing." (Star Trek: Communicator issue 134, p. 77) Mike Sussman commented, "The staff has talked about showing their evolution into the 'smooth-headed' and more cutthroat Klingons of the 'TOS' era. I don't know about the smooth foreheads, but I'd be interested in finding out why the Klingons never talked about honor in all the years Kirk dealt with them." (Star Trek: Communicator issue 139, p. 47) Supporting the decision to continue using the bumpy-headed Klingon makeup, Dan Curry said, "We're just doing the best work we possibly can and letting it speak for itself." (Star Trek: Communicator issue 135, p. 77)
An initial concept which Executive Producer Brannon Braga thought up for the series pilot of Enterprise, "Broken Bow", had Klingons attacking Iowa en masse. This was later changed to a single Klingon crash-landing in Broken Bow. (Star Trek: Communicator issue 135, p. 22)
The makers of Enterprise sought to make the early Klingons seen in that prequel series more primitive and rustic than the Klingons of later centuries, such as proposing (in "Broken Bow") that they "sharpen their teeth." In hindsight, Brannon Braga was uncertain how successful this endeavor was. "To be honest [...] I wonder if they look any different," Braga commented, with a laugh. "How do make a Klingon more Klingon-y? I think it was great in concept. I'm not sure if the Klingons ever were more gnarly." ("Broken Bow" audio commentary, ENT Season 1 DVD & ENT Season 1 Blu-ray)
Aware that there were many ways to depict the Klingons on Enterprise, Mike Sussman felt that the writing staff of the show's first season were "a little guilty" of taking "the least interesting choice" of how to portray them. He described this as showing them "behaving in exactly the same way as they will in the 24th century." (Star Trek: Communicator issue 139, p. 47) At the end of the first season, Brannon Braga similarly critiqued, "We did one Klingon show too many. So far, we seem to be helping them all the time. If we're going to do Klingons again, we need to make sure they're bad guys and start hinting at how they became our enemies. They haven't exactly been the titanic villains you might expect yet." (Star Trek: Communicator issue 139, p. 25)
Since writing staffers had these viewpoints, a concerted effort to show the Klingons in a more villainous light was made in the show's second season. This began with the episode "Marauders", of which Brannon Braga said, "We definitely wanted them to be bad guys. It was ultimately not as satisfying as it could have been, though." The later Season 2 installment "Judgment" picked up the "Marauders" plot thread of worsening relations between the Klingons and Starfleet. "It was an opportunity to delve into what Klingons were like during this period in history," said Braga. This episode had a more successful representation of the species. Even so, the penultimate installment of the season, "Bounty", was to feature the Klingons more than they are in the episode's final version, some of their involvement in the story having been substituted by the Tellarites. (Star Trek: Communicator issue 145, pp. 25, 28 & 31)
By the time of Enterprise's second season, the Klingon mythos had been built up over the years to such a point that Duras actor Daniel Riordan once remarked, "The whole Klingon legacy is so rich." Riordan was fascinated by the Klingons. A helpful aspect in shaping his performances as Duras was noticing that Klingons in general seem to be a mix of high intelligence with animal-like aspects. Of the latter quality, Riordan said, "Everything's real basic in terms of their bodies, their physical lives. Their emotions are excessive in violent terms." (Star Trek: Communicator issue 145, p. 55)
The later Enterprise episodes "Affliction" and "Divergence" explained the Klingon makeup differences, as Manny Coto and his team of writing staffers decided they did want to address the issue before Enterprise concluded its run. "It was an opportunity," stated Coto, regarding the option of telling a story that bridged the two variations of Klingon. (Cinefantastique, Vol. 37, No. 2, pp. 40-41)
Klingons of the alternate reality
|Warning! This section may contain spoilers for new Star Trek material.|
A new look for the Klingons – featuring masked helmets with ridges on the forehead – was created for a Klingon-centric deleted scene from the film Star Trek. Director J.J. Abrams was at first unsure how he wanted the Klingons in the film to look. Costume Designer Michael Kaplan recounted, "J.J. said, 'I don't really have an idea exactly what they should look like, but I do want them to be really, really, really scary.'" It was Abrams who devised using helmets, rather than creating full-facial Klingon makeups. ("Klingon Wardrobe" featurette, Star Trek (Three disc Blu-ray)) Despite the movie's script describing these masks, the script also refers to the Klingons as having "hideous faces" barely visible underneath. 
Once the helmets were designed, the Klingons' facial features were considered. Joel Harlow, who created the makeup designs for the Vulcans and Romulans in the film, stated, "The Klingons were a race that really wasn't addressed makeup-wise until, you know, maybe a couple weeks before we shot it." ("Klingons" featurette, Star Trek (Three disc Blu-ray)) At his suggestion, the makeup artists who collaborated on the movie did some preliminary work on designing the faces of Klingons from the alternate reality. "It was never really a given when we got started, but Joel said, 'I think we should sculpt a Klingon and have the pieces ready just in case,' so that's what happened," said Richie Alonzo, who worked closely with Harlow on the film. (Star Trek Magazine issue 172, p. 61)
The makeup included a small part of the brow to be seen through the helmet, as some of the Klingons were to be shown in close-up. ("Klingons" featurette, Star Trek (Three disc Blu-ray)) "Because wardrobe already had a helmet for the Klingons, we had to fit our makeup design under it, and make them work together," said Richie Alonzo. "You never really see what they look like, so we didn't want to come up with a specific look that we would be stuck with." (Star Trek Magazine issue 172, p. 61) Joel Harlow noted, "We knew that there had to be something there other than a paint job." Harlow, who sculpted the brow segment himself, felt it was fortunate that only a small portion of the brow had to be visually updated. The only other element of the makeup were faux beards. ("Klingons" featurette, Star Trek (Three disc Blu-ray))
Before it was even confirmed that his production company Bad Robot would be involved in a sequel to the Star Trek film, J.J. Abrams was highly interested in including Klingons in such a movie. (deleted scene "Prison Interrogation and Breakout" audio commentary, Star Trek (Special Edition & Three disc Blu-ray)) Once his connection to the film was announced, Abrams conceded that "it would be hard not to" introduce them in the alternate reality. (SFX, issue #200, p. 60) Screenwriter Roberto Orci also felt the pressure to incorporate the species in the sequel. "Some fans really want to see Klingons, and it's hard not to listen to that," he admitted. "The trick is not to do something that's been seen before just because you think it will be a short cut to likeability." (SFX, issue #200, p. 61)
Joel Harlow predicted that the Klingons would be featured in the sequel to the film Star Trek, saying, "That's gonna be a great challenge because the Klingons, I think, more than any other alien race beside the Vulcans, are known worldwide. So, how do you update that?" ("Klingons" featurette, Star Trek (Three disc Blu-ray)) Makeup Designer Barney Burman wanted to give the Klingons a new facial design for the sequel. "I would like to do the same kind of treatment on them that was done with the Romulans," he said, "and bring them into the new millennium." (SFX, issue #200, p. 60) In hindsight, Richie Alonzo remarked, "We thought it would be great to redesign the Klingons, and make them really cool-looking for the next film." (Star Trek Magazine issue 172, p. 61)
Lead Creature Designer Neville Page was also eager for the Klingons to return. In October 2010, he named them as "the one" species he would most like to tackle in the sequel. He proceeded to explain, "My approach would be to try and come up with something that's a unique look but is still a Klingon obviously. Because I think if I did them really tall like say 9' and instead of brown made them blue, I might get into a little trouble! But I would try think about them as real deal people -- and I know other designers have -- but really give them a history and a motivation. Understand why they're dressed the way they are. Understand their rationale for long hair and facial hair. Make sense of those physical features which they typically have, which are the ridged foreheads." Page added that, not being entirely sure how he would tackle the species, he had started contemplating ways to distinguish Klingon races; "There are different physiological ticks even in the Klingon world. Maybe they are all brown, but the ridges are the African ones, the fewer ridges are the Asian ones. I don't know." 
Since the alternate-reality Klingons had been all but consigned to a single deleted scene, the makers of Star Trek Into Darkness were given free reign to reinvent their look. This opportunity was made the responsibility of Neville Page, Michael Kaplan and makeup department head David LeRoy Anderson. Richie Alonzo concluded that, for many of the makeup artists who had worked on the previous movie, the chance to redesign the Klingons "never materialized." (Star Trek Magazine issue 172, pp. 62 & 61)
The aforementioned sense of creative freedom drove Neville Page's designs. David Anderson reported, "Based on the versions that I saw Neville produce, I think he was not committed to anything, and free to explore a new direction." Heather Langenkamp, Anderson's partner at makeup shop AFX Studios, added, "Neville generated lots of amazing ideas about their appearance." (Star Trek Magazine issue 172, pp. 62 & 63) According to Anderson, Page and J.J. Abrams "got pretty far out there" with their Klingon facial concept designs before "it started to come back." Anderson elaborated, "Everyone was trying to pay homage to the fans' idea of the real race while wanting to innovate something new...." (Empire, Issue 287, p. 87) Indeed, Anderson discovered that he also didn't want to overly alter what had become an iconic look. “It’s a real balancing act," he noted. "You don’t want to stray too far, but you also don’t want to go back and cookie-cut the exact same thing. There have been a lot of advances and we have the opportunity to do a new, fresh pass without losing anything."  Page himself stated, "As much as we wanna bring something fresh to the table, we also want to make sure that it is respectful to the culture. I studied [the] Klingon [language] quite a bit, and spoke to a lot of [Klingon fans] [....] There was this one treatment, a piercing element that the Klingons have, and few would recognise it, but those who are serious fans will catch it." 
The actors playing Klingons in Star Trek Into Darkness were cast if they looked intimidating. Props Master Andrew Siegel remembered, "We thought, ‘Okay, these guys should be badass.’ We cast all real imposing guys and they are scary.”  The notion of making the Klingons brutal-looking reflected on elements of their culture. "That was something I gravitated towards," acknowledged Siegel. "The main thing for me was: 'What are these characters like?' They are incredibly barbaric. I wanted all of their props to reflect that." (Star Trek Magazine issue 173, p. 79) Despite the attempts to aesthetically highlight their barbarism, an effort was made to make the Klingons look somewhat appealing. Neville Page said, "One thing I tried to do with the Klingons, which was a tough one, is make them sexy: a beautiful-ugly group of men. I think we got it. Not that the previous actors were ugly, but it was a very conscious choice of who we cast, a very conscious sculpting of the Klingon form to make them look sexy. In a way."
At a point when production was well underway, the first Klingon facial sculptures were digitally created, which Neville Page did using ZBrush. Not entirely happy with the original sculptures, David Anderson tweaked the designs. "David put little changes on them," said Heather Langenkamp. Because ongoing production on the film meant that Anderson was extremely busy, however, he hired makeup artist Earl Ellis to tweak the designs. "Neville's artwork was beautiful," commented Anderson, "but it was translating into a very heavy makeup that would have concealed all of the features on the performer if we used that sculpture." (Star Trek Magazine issue 172, pp. 62 & 63) Anderson also clarified, "When we studied the 3D rendering, we realized the proportions would have resulted in areas of makeup that were three or four inches thick. That would have limited the actor's ability to perform." (Cinefex, No. 134, p. 85) Ellis concurred, "The designs were tending to look a bit more mask-like, and we really needed a makeup approach." (Star Trek Magazine issue 172, p. 62) The group specifically realized that, by using massive blocks of foam rubber on the faces of the performers, they would end up making all the actors look exactly the same, whereas the creative team intended for each individual member of the species to be different-looking. 
Earl Ellis thereafter contributed to the design process. Continued David Anderson, "I said, 'I'm afraid the flavor and essence of the Klingons is not coming across here,' so Earl looked at the illustrations, and immediately understood what they represented, what we could use, and what to leave behind. He was able to translate Neville's ZBrush creation into an actual functioning makeup that allowed the actors' performances to come through." (Star Trek Magazine issue 172, p. 62) In essence, the makeup team came up with the solution to their predicament by endeavoring to leave the Klingon faces more exposed and use multiple prosthetic pieces, allowing for more expressive facial movements.  Ellis himself recalled, "When Dave showed me the designs, I recognized a lot of design elements that had been put into these characters. If you look at any of the episodes from the past 20 years, they have a certain color scheme that says, 'Klingon,' and you can't go too far from that. So I recognized those elements, but the design was sleeker, and more elegant. Not just some bestial character [....] The less you put on somebody, and the thinner the pieces, the better they can act, so that's the approach we took [....] It's tough to do the Klingons, because they kept changing over the years." (Star Trek Magazine issue 172, p. 63)
As the Klingon helmets had impressed J.J. Abrams to a great degree and since they had already been paid for, the helmets actually appear on-screen in Star Trek Into Darkness. (Star Trek Magazine issue 172, pp. 98-99 & 63) Earl Ellis foresaw some potential difficulty with trying to combine the Klingon head prosthetics with the helmets. "That would have limited the size of the heads," he speculated, "but because I took a makeup approach, that was fine." (Star Trek Magazine issue 172, p. 63)
The filmmakers were highly satisfied with the new Klingon makeup design for Star Trek Into Darkness. "Once Earl finished his sculpture of the Klingon character on our two actors, we brought them to set for a show and tell, and J.J. Abrams loved them," David Anderson reminisced. "There was no critiquing; it was just, 'Yes, we've got our Klingons!' He could see that they were two completely different beings, but from the same planet, and they were really nice, subtle and thin makeups." Heather Langenkamp commented, "Of all the make-up we did, we're most proud of the Klingons. It's really powerful and fantastic. There's something very regal about it." Ellis not only described the new Klingons as looking "more elegant" than they had in the past but also reckoned, "I think the fans will be very happy with them." (Star Trek Magazine issue 172, p. 63)
Nowadays, there is once again no explanation for the introduction of redesigned Klingons. Earl Ellis concluded, "You just have to accept them for what they are. There's no real reason why they should look the way they do now, compared to the original series, but they still have all the elements that say 'Klingon'." (Star Trek Magazine issue 172, p. 63)
When quizzed about plans for a third film produced by Bad Robot, Damon Lindelof was noncomittal about whether Klingons will return but admitted, “You can never see enough Klingons, and I think in this film [Star Trek Into Darkness] we’ve given the audience a little taste, but there’s also a promise that there’s a larger conflict on the horizon, and that would be fun to see." 
Popular culture and trivia
The popularity of the Klingons has grown over time. In 2002, Richard Arnold mused, "For good and bad, the Klingons have become really prominent in Star Trek and in Star Trek fandom, in spite of having made only eight appearances on the original series." (Star Trek: Communicator issue 139, p. 70) Noting the impact that the Klingons had on fans of the original series, D.C. Fontana laughed, "They suddenly became really popular for us!"  At the time, the Klingons were so popular that, after William Campbell played Koloth in "The Trouble with Tribbles", he received fan mail that included people writing about the Klingon eyebrows he had worn and the children in Campbell's neighborhood teasingly referred to his wife as "Mrs. Klingon." (The World of Star Trek, p. 120)
The portrayals of Klingons in the original series have also been successful with production staffers. As a fan of the original series from the second half of its first season onwards, Robert O'Reilly had long-standing aspirations to portray a Klingon. "If you had asked me at any time throughout the years which role I wanted to play on Trek," he admitted, "'it would have been a Klingon." When asked why he had this enduring interest in Klingons, O'Reilly responded, "Well, I really like bad guys. I like being able to go a little over-the-top with my acting and have fun with it. I knew I could do a very good job with a Klingon role because I could bring in my Shakespearian background and use my accents in different ways." (Star Trek: Communicator issue 104, p. 53) David Gerrold also appreciates the Klingons from the original series. He raved, "I just love those Klingons! They're just... they're so self-righteous and arrogant and pompous. You just want to stick pins in them, to watch them explode! But they're the perfect foil for Kirk [....] The Klingons are comic villains of the best sort and, I mean, if you look at the way the Klingons have been played ever since, yes they're villains, but they get some of the best lines, they get the funny lines." As an example of what he meant, Gerrold cited Gorkon saying, "You have not experienced Shakespeare until you have read him in the original Klingon," in Star Trek VI: The Undiscovered Country. Dave Rossi remarked, "They're no less savage and tricky [than the Klingons in later Star Trek productions] [....] The Klingons in the original series are deliciously clever and backstabbing and ready to kinda stick you with a shiv at any minute." ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray)
As the underground popularity of Star Trek increased in the years when it was no longer aired after the making and broadcast of the original series, there was a strong portion of fandom that was so passionate about the Klingons that an extensive backstory universe started to grow in the show's absence. (Star Trek: Communicator issue 114, p. 26) Richard Arnold pointed out, "With Klingons in four of the [first] six films, there was obviously something about them even then." (Star Trek: Communicator issue 139, p. 70) Although William Campbell characterized the Klingons generally as "the perfect adversaries," he was not pleased with their redesign in The Motion Picture, observing, "When people saw the first movie, they said, 'What the hell is that?' You can't have a guy with a head like a crab become a rival.' " (Starlog, #138, p. 34) Robert Justman was extremely pleased to view how the Klingons are portrayed in The Motion Picture, later commenting, "I was entranced when I first saw the movie and I saw those wonderful bony protuberances. I was thrilled. They were so imposing, frightening, awe-inspiring. It seemed to free the actors so they could shake off their inhibitions and go over the top portraying their characters." (Star Trek: Communicator issue 114, pp. 26-27) Because Leonard Nimoy has always been highly interested in the Klingons (which he termed "our favorite villains") and their culture, Nimoy was regretful that the films he was involved in didn't use all the potentialities of the Klingons that he believes they hold. He commented, "To this day, I wish I could have done a serious study of Klingon culture in one of our films; I think they're marvelous 'dark side' adversaries." (I Am Spock, hardcover ed., pp. 313 & 223)
The response of fans to initial news that the Klingons were to be excluded from The Next Generation was an influence on the alteration of this plan. (Star Trek Monthly issue 10, p. 50) The Klingons gained even more fans as aggressive allies of the Federation than they had as its enemies. (Star Trek: The Original Series 365, p. 139) There were early criticisms, though, that Worf was too dissimilar from other Klingons, to which Michael Dorn responded, "If you're expecting a race to remain completely unchanged over time, then you're being rather narrow-minded." (The Official Star Trek: The Next Generation Magazine, vol. 15, pp. 46-47) One initially skeptical fan was Ronald D. Moore, who was at first doubtful that the Klingons as allies could be as fun as they had been as foes. He was, however, excited by the Klingon-related possibilities which the addition of Worf suggested. For example, Moore eagerly anticipated seeing "the Klingon version" of such episodes as "Amok Time" or "Journey to Babel", which had established much about Vulcans and their culture. (Star Trek: The Next Generation 365, p. I1) Recalling his opinion of the Klingons at the time he wrote "The Bonding", Moore stated, "I thought they were a really cool species." ("The Bonding" audio commentary, TNG Season 3 Blu-ray) Dave Rossi had a criticism about the TNG Klingons. "It's kind of a shame," he lamented, "that [...] for instance, in Next Generation, Commander Worf [...] just kind of became a measuring stick for how bad the next bad guy was. A bad guy would show up and if he could punch Worf in the face and knock him out, you went, 'Wooh, that guy was bad; he beat up a Klingon!' But in doing so, it kinda defanged the Klingons in a lot of ways. That never happens in the original series." ("Errand of Mercy" Starfleet Access, TOS Season 1 Blu-ray)
Director Cliff Bole – who worked on such Klingon-inclusive episodes as "The Emissary", "Redemption", "Unification II", "Aquiel" and "Suspicions" – valued the considerably overboard nature of the Klingon species and the freedom for inventiveness which they allowed. "I think the Klingon shows are fun to do," he remarked, "because you can go a little broad with them. Who the hell knows what a Klingon is anyway? Who knows how Klingons make love?" (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 182) The Klingons – including villainous sisters Lursa and B'Etor – were still enormously popular at the time of Star Trek Generations' production. This led B'Etor actress Gwynyth Walsh to proclaim, "There's a tremendous curiosity and delight in Klingons among the fans and it spills over to us [meaning herself and Lursa actress Barbara March]." (Star Trek Generations - Official Movie Souvenir Magazine) Somewhat explaining why the Klingons were originally made antagonists in DS9 Season 4, Rick Berman described them as "the villains that people love to hate." Shortly before that season, Michael Dorn mused about the Klingons, "Everybody admires their sense of honor. Even though it may have been passé in the years past, it's definitely one of those things that people recognize and respect now. Klingons have a sense of honor, and of going for it, and being up front, and telling it like it is. And I think that's what people like about them." (Star Trek: Communicator issue 104, pp. 9 & 59)
Even if he was no longer part of the Star Trek franchise, Robert O'Reilly was very happy that the Klingons were a part of Enterprise. He characterized their return as "what I like most" about the series and said he was pleased "as long as Klingons are back." (Star Trek: Communicator issue 145, p. 54)
By 2010, the Klingons had become the most popular alien species from the entire Star Trek franchise, Vulcans notwithstanding. (Star Trek: The Original Series 365, p. 139) Neville Page disclosed that, upon researching the culture around Klingons prior to crafting their facial redesign for the 2013 film Star Trek Into Darkness, he talked to "the Klingon people at Comic-Con, people who role-play that world."  Theorizing about the appeal of such an activity, Marc Okrand, the inventor of Klingonese, offered, "When you're [pretending to be a Klingon], you can do things that you can't do if you're human. You can get away with being demanding and bossy and just saying what you want [...] [which] polite society prevents you from doing. You can step back from that." (Star Trek 30 Years, p. 66)
Michael Dorn talked about how Klingons have been represented as multi-dimensional, suggesting, "You know there's a lot of Klingons that definitely don't have any honor and definitely don't have any morals or any scruples. So, the lesson you have to learn is there are no absolutes [....] You can't just go, 'Okay, I'm a Klingon and I'm going to do this despite everything about you." (Star Trek: Communicator issue 104, p. 59) Concerning the moral ambiguity, Robert O'Reilly considered, "Maybe that's the key. Maybe that's what 'the Klingon way' is all about; a constant redefining of what it really means to be a true Klingon warrior." (Star Trek: Communicator issue 104, p. 54)
One production staffer who enjoyed working with Klingons, on both DS9 and Enterprise, is James L. Conway; from the episodes he directed, the ones that included Klingons are "The Way of the Warrior", "Shattered Mirror", "Apocalypse Rising", "Broken Bow" and "Judgment". "I love doing scenes with Klingons," he enthused, "I [did] a lot of Klingon scenes over the years, on Star Trek, and I never got tired of it. It was so much fun to do." ("Broken Bow" audio commentary, ENT Season 1 Blu-ray)
Over the years between The Motion Picture and "Trials and Tribble-ations", several fan-devised theories for the discrepancies between the two main forms of Klingons were postulated. (Cinefantastique, Vol. 37, No. 2, p. 40) One suggestion, relayed by Richard Arnold, was that the two variants of Klingon were from different hemispheres of the Klingon homeworld than one another. (Star Trek: Communicator issue 104, p. 12) The decision to maintain the Klingons' head ridges for Enterprise proved extremely controversial among the fans. (Star Trek: Communicator issue 135, p. 74) However, even individual Klingon makeup elements (Worf's head, for example) changed from episode to episode. Besides Michael Dorn and Roxann Dawson, other Star Trek cast members who wore the full Klingon makeup include Avery Brooks, Colm Meaney, LeVar Burton, Rene Auberjonois, Tim Russ, Kate Mulgrew, Ethan Phillips, and Scott Bakula.
Following the return of Kor, Koloth and Kang in "Blood Oath", fans wanted those Klingons to return, despite Koloth and Kang dying in the aforementioned episode. "Of course, a lot of them have speculated about how they could bring us back together again – such as the fact that maybe we weren't completely dead because we have two hearts," acknowledged William Campbell. He tended to think it wouldn't be surprising if the trio of Klingons did indeed somehow make a comeback, despite this not ultimately happening. (Star Trek Monthly issue 11, p. 54)
Over the years, multiple Klingons were portrayed by Star Trek veteran actor Vaughn Armstrong. These include not only Korris in "Heart of Glory" but also Korath in Star Trek: The Experience and VOY: "Endgame" as well as a Klingon captain in ENT: "Sleeping Dogs". He once envisioned what Klingon children might be like. "They had all these warlike ridges and body armor, and I could just picture them in the backyard as children playing with a goat," he imagined, "smacking their foreheads up against the goat's or against each other." (Star Trek: The Magazine Volume 2, Issue 9, p. 44)
The only time the Klingon symbol is seen in the original series is in "Elaan of Troyius", and the high spire is actually facing right, not straight up as the subsequent versions are. Also, on the original Klingon ship model (the camera angles never showed it on the series), it was facing to the right there as well. It was probably meant to be that way originally, but series executives and concept designers likely found it looked better pointing straight up.
The infamous Klingon saying, "Today is a good day to die," actually originated from the Lakotan warrior Crazy Horse, while the proverb, "Revenge is a dish best served cold," paraphrased by Khan in Star Trek II, is actually a saying of the Pashtun people of South Asia.
A political analogy
On 10 January 2007, Congressman David Wu made a speech, on the House of Representatives floor, referring to George Bush's staff as Klingons, with regard to the Iraq War. Wu, an admitted fan of Star Trek, said he was making a reference to the title of James Mann's recent book Rise of the Vulcans: The History of Bush's War Cabinet (ISBN 0670032999). In the book, Mann writes that "Vulcans" is a nickname that President Bush's foreign policy advisory team in the 2000 campaign gave itself, originating from a large statue of the Roman god Vulcan in Bush adviser Condoleezza Rice's hometown of Birmingham, Alabama.
Wu said that – unlike "the Vulcans of Star Trek", who "make decisions based on logic and fact" – Rice and her cadre behave more like the warlike Klingons, saying, "There are Klingons in the White House." Wu continued that – unlike "real Klingons", who are also known as fierce warriors – those in the White House "have never fought a battle of their own." He concluded, "Don't let faux Klingons send real Americans to war."
On 16 January 2007, comedian Jon Stewart dedicated a short segment of The Daily Show with Jon Stewart to talk about this speech. He was joined in this discussion by Leonard Nimoy and George Takei (Spock and Hikaru Sulu, respectively). In the discussion, Nimoy stated that the analogy was weak, citing that – while Klingons are warlike – they adhere to a strict code of honor.
In the novel Summon the Thunder, part of the Star Trek: Vanguard series, the Klingons who had a Human appearance (descendants of the victims of the Klingon Augment virus) are referred to as "QuchHa", or "the unhappy ones". They usually served in their own units although they also were known to mix with the rest of the fleet on occasion.
"Against Their Nature", the first installment of "Star Trek: Klingons - Blood Will Tell", an IDW Comics series which tells the stories of "Errand of Mercy", "The Trouble with Tribbles", "A Private Little War", and "Day of the Dove" from the Klingon point of view, suggests that, while Phlox and Antaak's cure removed Augment strength and Augment intelligence, those affected retained the superior ambition of Augments, and as such these Klingons were largely responsible for the Empire's expansion in the century between Enterprise and TOS, eventually becoming powerful enough to achieve a majority on the High Council.
In the novel Pawns and Symbols, Klingons are discovered to be color-blind in the Human sense, unable to distinguish red from black. It is also discovered that their vision extends into the ultraviolet, to 32,000 Ångströms.
In the novel Ishmael, the Klingons are described as having been economically conquered and uplifted by the Karsid empire. The Klingons then rebelled and overthrew the Karsids, obtaining their high technology. This was given as one reason for why the Klingons were the way they were, and also how they could have developed star-faring technology given their current social structure.
In Star Trek Online, the Klingons are once again enemies with the Federation by 2399, having taken advantage of the Romulans by conquering much of their territory in the wake of the death of Shinzon and then the destruction of Romulus. The Klingons have also conquered the Gorn, the Orions, and the Nausicaans. Evidently, Klingons are seen joining Starfleet, if unlocked.