(covers information from several alternate timelines)
Sarek of Vulcan spent most of his life in service of the Vulcan people, as an ambassador and representative on the Federation Council. He was also well known as the father of noted Starfleet officer (and fellow diplomat) Spock and the former husband of the Earth woman Amanda Grayson.
Sarek's accomplishments as an ambassador of the Federation included the Coridan admission debate of 2268 before the Federation Council, early treaties with the Klingon Empire (Treaty of Alliance) as well as with Alpha Cygnus IX, and his incredible effort to bring about a Federation-Legaran treaty, which began in 2273, and concluded in 2367. (TOS: "Journey to Babel"; TNG: "Sarek") Though he briefly retired shortly before the Babel Conference in 2268, Sarek's involvement in the Coridan admission debate included attending multiple council sessions, at least one of which was before the conference on Babel. (TOS: "Journey to Babel")
The son of Skon, Sarek was born in 2165 and willingly tutored by his own father. (Star Trek III: The Search for Spock; TNG: "Sarek"; TOS: "Journey to Babel") During his childhood, he had a pet sehlat named I-Chaya. (TAS: "Yesteryear")
Sarek's first child, Sybok, was born to a Vulcan princess. (Star Trek V: The Final Frontier) Sometime after she died, while serving as Ambassador to Earth, Sarek wed a Human female named Amanda Grayson. (Star Trek V: The Final Frontier; TOS: "Journey to Babel") A later recollection of Sarek's was that he had married her because, "at the time, it seemed the logical thing to do." (TOS: "Journey to Babel")
Amanda gave birth to Sarek's second son, Spock, three years after Sarek married her. (TOS: "Journey to Babel"; TAS: "Yesteryear") Upon first holding him, Sarek remarked that the newborn Spock was "so Human." (Star Trek V: The Final Frontier) Sarek passed his pet sehlat I-Chaya on to Spock, and raised him and Sybok as brothers. (TAS: "Yesteryear"; Star Trek V: The Final Frontier) When Spock was aged seven, Sarek was involved in arranging for him to wed T'Pring, later in life. (TOS: "Amok Time") Sarek also gave Spock his first lesson in computers. (TOS: "Journey to Babel") However, as a seven-year-old, Spock was occasionally bullied by Vulcan children who claimed that Sarek had brought shame to Vulcan by marrying a Human. (TAS: "Yesteryear")
In the alternate timeline wherein Sarek's ambassadorial career was different to how it was in the prime timeline, Sarek separated from Amanda Grayson, following Spock's death, and did not remarry after Grayson died. (TAS: "Yesteryear")
In 2250, Sarek broke off his relationship with Spock, when the latter decided to apply to Starfleet Academy instead of the Vulcan Science Academy. Sarek wanted Spock to follow his father's teachings, just as he himself had followed the teachings of his own father. (TOS: "Journey to Babel")
In 2266, Spock noted Balok as being reminiscent of his father, even stating – at one point early in the first contact between the First Federation and the Enterprise – that he regretted not having learned more about Balok. (TOS: "The Corbomite Maneuver")
In 2267, while Captain James T. Kirk was attempting to aggravate Spock by making up false insults, he insisted that Sarek had been "a computer." (TOS: "This Side of Paradise") Later the same year, Spock evoked the authority of his father (as well as their male ancestors), while making an unsuccessful attempt to persuade T'Pau to prevent him battling Kirk in a kal-if-fee. (TOS: "Amok Time")
During the council session immediately before Sarek's brief retirement, Sarek met and debated with Tellarite Ambassador Gav, winning their argument. His short period of retirement thereafter was due to concerns other than his age. Shortly before he left Vulcan with his wife and a group of aides, Sarek suffered two heart attacks. He did not inform his wife of these incidents, though his physician prescribed Benjisidrine for the condition. He didn't speak with Spock again until the Coridan debate of 2268 (en route to the Babel Conference), when Sarek survived a series of heart attacks and surgery, only after a transfusion of rare T-negative blood from his son. (TOS: "Journey to Babel")
Sarek and Spock remained on good terms as the Klingon détente bloomed in the 2280s. In 2285, however, Spock was left for dead on the Genesis Planet after sacrificing his life to save the USS Enterprise. Sarek traveled to Earth, where he convinced James T. Kirk, now an admiral, to retrieve his son's body and pushed for a fal-tor-pan fusion of Spock's katra and body; although aware of the dangers and complications of the ritual, Sarek stated that his logic was uncertain where his son was concerned. (Star Trek III: The Search for Spock)
Three months later, Sarek finally apologized to Spock for his original opposition to Spock's decision to join Starfleet, recognizing Spock's friends as people of good character. (Star Trek IV: The Voyage Home)
In 2293, Sarek suggested that Spock initiate negotiations for a proposed Federation-Klingon Alliance with Chancellor Gorkon, hoping to bring together the two lifelong enemies after the destruction of the Klingon moon Praxis. That almost didn't happen, for Gorkon was assassinated. Captain Kirk and Dr. Leonard McCoy were arrested by the Klingons, having been framed for the chancellor's murder. Sarek was present in the Federation President's office when several attempts to stop Kirk and McCoy being tried in Klingon territory were outlined, but he had to concede that the Klingons were within their legal rights and that the Federation could not interfere in their due process. Kirk and McCoy, with Spock's assistance, eventually escaped from imprisonment on Rura Penthe, and they arrived at the Khitomer Conference in time to prevent the assassination of the Federation President. (Star Trek VI: The Undiscovered Country) Afterwards, Sarek was involved with the Khitomer Accords, and further helped the Federation and Klingon Empire establish their almost one-hundred-year peaceful co-existence. (TNG: "Sarek")
Sometime after the Khitomer Conference, Spock left Starfleet and became an ambassador and representative of the Vulcans to the Federation. It is suspected he and Sarek were involved in few diplomatic missions. The two, however, split again over the Cardassian issue of the 24th century. Sarek was also dismissive of Spock's friendship with Romulan Senator Pardek, who he had met at Khitomer, and the prospects for a lasting Federation-Romulan peace. (TNG: "Unification I") By that time, Amanda had died, and Sarek had married another Human woman, named Perrin. Sarek was present at his son's wedding before they again stopped speaking to each other; it was at that event that Sarek first met Jean-Luc Picard. (TNG: "Sarek")
In 2366, Sarek was diagnosed with Bendii Syndrome. He was meanwhile negotiating a treaty with the Legarans. As his emotional control was incredibly weak, he mind-melded with Captain Picard at the suggestion of his wife, Perrin. Sarek was then stable enough to conclude the negotiations, which had taken ninety-three years. He told Picard, "We shall always retain the best part of the other inside us." (TNG: "Sarek")
In 2368, Sarek died at the age of 203, in his home on Vulcan. (TNG: "Unification I") When meeting with Ambassador Spock on Romulus, Picard learned that Spock and his father had never mind-melded, and offered Spock the chance to share what Sarek had shared with him. The meld passed along Sarek's true feelings of love and admiration for his son that he had never allowed himself to convey in life. (TNG: "Unification II")
In 2370, after Julian Bashir told Elim Garak, "Before you can be loyal to another, you must be loyal to yourself," the Cardassian attributed the quote to Sarek, but it was actually Bashir's own. (DS9: "Profit and Loss")
Casting and first episodes
The first canonical evidence of Sarek was a very vague reference in "Where No Man Has Gone Before", an allusion that was specifically Spock mentioning "one of [his] ancestors" who had married a Human female. From then on, Sarek was usually referred to in a more direct fashion, consistently described as Spock's "father" in later episodes of the first season.
A description of Spock in an early-1966 publicity booklet released by NBC (and reprinted in Inside Star Trek: The Real Story) suggested that his father not only was an extraterrestrial who had married a woman from Earth but also was possessed of "a precise, logical turn of mind" which Spock inherited.
During the run of the series, Sarek was referred to in the past tense in all but one episode; in "The Squire of Gothos", Spock tells Trelane, "My father is from the planet Vulcan." Sarek's occupation as an ambassador was first established in "This Side of Paradise", whose teleplay was written by D.C. Fontana. This reference was a prime motive for Fontana later writing "Journey to Babel". (Star Trek: The Magazine Volume 1, Issue 2, p. 84) While she did so, Fontana conceived the rift between Sarek and Spock, including it in the episode. (Starlog issue #118, p. 18) It was also in that installment that Sarek was finally named.
Sarek's name was inspired by a memo in which Robert Justman proposed to Gene Roddenberry that Vulcan names should be no longer than five letters, begin with "S", and end with "k". (I Am Spock, hardcover ed., pp. 72 & 73)
The script of "Journey to Babel" included the following description of Sarek: "Because of Vulcan longevity, it is impossible to tell Sarek's age. He appears no more than late forties. He is actually one hundred two – middle age for a Vulcan [....] Sarek's speech is almost without inflection." (Star Trek Magazine issue 155, p. 40) A scene cut from the same episode's final draft script would have established that Sarek's father was himself a well-renowned Vulcan ambassador, named Shariel. (The Star Trek Compendium, 4th ed., p. 89)
Mark Lenard, the actor who primarily played Sarek, was cast in the role apparently because he had made a good impression with the producers by playing the similarly pointed-eared Romulan commander in "Balance of Terror". (I Am Spock, hardcover ed., p. 71) D.C. Fontana recalled, "When we were casting in second season for 'Journey to Babel' and I was then the story editor and I had written that script, Gene said, 'What do you think about Mark Lenard for Sarek?' and I said, 'Whoopy-do! Let's go!' You know, I was all for it. He was perfect, again." ("Balance of Terror" Starfleet Access, TOS Season 1 Blu-ray) Lenard was forty-three when he was cast for the part in "Journey to Babel". (Star Trek: The Original Series 365, p. 218)
Mark Lenard was artificially aged to play Sarek for the Vulcan's introductory appearance. "In those days," he reflected, "they needed to fix my hair up with a little grey and they put wrinkles around my eyes, and then, of course, the ears." (Star Trek IV: The Voyage Home - The Official Poster Magazine, p. 56)
By way of research before playing Sarek, Mark Lenard quizzed Spock actor Leonard Nimoy, shortly after they first met. "Mark was very curious about Vulcans and wanted to know as much as he could about them," Nimoy recalled, "so we discussed this at length on the set." Lenard found it easy to perform the Vulcan salute and helped devise the intimate ritual of Vulcan finger-touching. (I Am Spock, hardcover ed., p. 71) He also developed a large degree of knowledge about the character of Sarek. In a 1987 interview, Lenard mused over Sarek's personality and his reaction to Spock opting to join Starfleet rather than the Vulcan Science Academy, commenting, "Sarek, like many people of strength and societal importance, believes in the superiority of the Vulcan way [....] And the fact that Sarek's son, whom he nurtured and taught, the one who expresses the best that is the Vulcan society, should go off and share all this knowledge with others hurt him deeply, I think." (Starlog issue #117, p. 46)
The fan response to Sarek was immediate and, for two weeks after the initial telecast of "Journey to Babel", Mark Lenard's fan mail was even more numerous than that being sent to Leonard Nimoy. (The World of Star Trek, 3rd ed., p. 146) Nimoy himself also approved of how Lenard portrayed Sarek in Star Trek: The Original Series, later stating, "Mark had a real sense of the dignity and authority the character needed." ("To Boldly Go... Season Two", TOS Season 2 DVD & Blu-ray) Nimoy also expressed, "The great dignity that he brought to the role of Sarek earned him a permanent place in the hearts of Star Trek fans." (I Am Spock, hardcover ed., p. 71)
In a deleted scene filmed for "Elaan of Troyius", it was revealed that Sarek was an accomplished musician. He placed first in an all-Vulcan music competition; second place was awarded to Spock. (The Star Trek Compendium, 4th ed., p. 197; )
The character of Sarek proved so popular that D.C. Fontana brought him back for her 1973 Star Trek: The Animated Series episode "Yesteryear". (Star Trek Magazine Special 2015, p. 72) In the script of that installment, Sarek was initially described as "distinguished looking". The same teleplay later characterized him as having a "deceptively quiet, unhurried voice" that Spock "would recognize in an instant anywhere." The "Yesteryear" script went on to further describe Sarek thus; "He is a tall, broadshouldered Vulcan, obviously in physical trim. His sharply planed, strong features and deepset eyes make him attractive." Before Mark Lenard was available for that animated episode, James Doohan recorded the character's lines of dialogue for the installment. It was intended that his voice would serve as Sarek's in the episode, though Lenard's voice was thereafter looped over Doohan's recordings. (Star Trek: Communicator issue 119, p. 78)
Initial film appearances
In a story written by Jon Povill and proposed to become the first Star Trek film, a societal upheaval on Vulcan included one of the Vulcans arguing that Sarek should be confined. (Lost Voyages of Trek and The Next Generation, p. 11) Sarek was also to have been mentioned by name during the Kolinahr scene in Star Trek: The Motion Picture and was included in the shooting script for that movie, though not in the film's final version. 
Sarek's inclusion in Star Trek III was arranged by Harve Bennett. (Starlog issue #117, p. 49) In an early story outline that Bennett wrote for the film, Sarek was a prime minister on Vulcan during a politically critical situation, as a Vulcan faction had reverted to the primitive behavior of their ancestors. Upon the Enterprise visiting the planet, Sarek rescued a landing party from an attack by the rebellious faction, though his attitude toward the newcomers was somewhat cold and angry. Sarek told Kirk, in the prime minister's quarters, that many Vulcans were unhappy with the Federation having such a powerful weapon as the Genesis Device; though elected prime minister as a peacemaker, Sarek was barely retaining order. It was also at this point, rather than on Earth, that Sarek admonished Kirk for not returning Spock's body to Vulcan and inquired as to how Kirk had known Spock had not been in a transcendental state. Sarek finally instructed Kirk to bring him Spock, and advised the admiral to hope that he would still be there when Spock arrived.  Although Sarek additionally appears in the film's conclusion, this was not true of the outline. (Star Trek: The Magazine Volume 3, Issue 8, p. 30; Trek: The Unauthorized Story of the Movies, p. 84)
Mark Lenard was very happy to reprise his role of Sarek in Star Trek III. He later reminisced, "I was given a wonderful part in the film [....] [As director, Leonard Nimoy] really gave me some great opportunities to bring my character to life; I got to play an equal part in giving ideas for Sarek." (Star Trek: Communicator issue 137, p. 48) With Lenard having become a frequent guest at Star Trek conventions by that point, fans rejoiced when he reappeared as Sarek in the movie. (Star Trek Compendium, 4th ed., p. 89)
Sarek's chat with Spock in Star Trek IV: The Voyage Home was conceived a little differently from how it turned out. In the earliest version of the discussion, Sarek basically admitted that, though he would never understand Spock's half-Human nature, he nonetheless accepted him. "It was originally much more bonding, but they [the producers] removed about half a page of dialogue, which changed things quite a bit," related Steve Meerson, who was originally assigned to co-write the film's script. (The Making of the Trek Films, 3rd UK ed., p. 64)
Sarek was talked about amid a story conference in which William Shatner, Harve Bennett and David Loughery tried to work out the details of the plot for Star Trek V: The Final Frontier. At one point, Shatner voiced interest in Sarek's motives for marrying Amanda, following the death of Sybok's mother. Even though Loughery reminded Shatner that this event had been commented on in the series, Loughery did not consider this usable story material for the film, finding it superfluous to the storyline. Despite this, Shatner again briefly mentioned Sarek's relationship with Amanda as a potential element of the movie's backstory. The group briefly contemplated that Sarek may have fathered Sybok during his marriage to Amanda, bearing the child out of wedlock to another woman, but the team then opted for Sybok having been born before Sarek married Amanda. Sarek was also considered as having motivated Sybok's departure from Vulcan, out of fear regarding Sybok's influence on Spock. An alternative to this involved both of Sarek's children choosing to leave but Sarek then confronting Spock with an implied threat that, if Spock did decide to depart, he would be completely disowned by his own father. (Captain's Log: William Shatner's Personal Account of the Making of Star Trek V: The Final Frontier, pp. 64 & 65)
One exception to Mark Lenard appearing as Sarek was in Star Trek V, wherein young Sarek was played by Jonathan Simpson, though voiced by Lenard. That film's eventual backstory concerning Sybok and Sarek's relationship with a Vulcan princess has long been considered apocryphal by some sources, which included Gene Roddenberry.
Depictions in TNG and final film
Sarek's initial reappearance on Star Trek: The Next Generation originally came about because Gene Roddenberry – having at first been determined to separate that Star Trek series from the original one – became confident to try a character crossover between the series. This was due to The Next Generation gaining popularity by its third season. In hindsight, Mark Lenard reminisced, "I was in Gene's office and he said, 'You know, it's about time that Sarek comes back. After all, Vulcans age very slowly.' I thought that was a good way to put it, not that they live a long time, but that they age very slowly – because it took them another year and a half before they found a script for me to play!" (Star Trek - Where No One Has Gone Before, paperback ed., p. 136)
Although Sarek's previous appearances in the third and fourth Star Trek films could have been the last times he was featured in the franchise, Marc Cushman had other notions in 1988, when Gene Roddenberry heard his idea for a plot involving the character. Cushman pitched Roddenberry a story in which the Vulcan ambassador had to be brought out of retirement for one final mission but was, unbeknown to those around him, in the initial stages of a debilitating neurological illness. (Star Trek Magazine Special 2015, pp. 72 & 74) Early in TNG's second season and six months after the 1988 Writers Guild strike began, Roddenberry notified Cushman that, although he wanted to do something with the story, he was reconsidering whether the plot's main character was to be Sarek. "He asked me to take Sarek out of the script," said Cushman, "and make it a different Vulcan, or a member of a different race that has telepathic abilities." Roddenberry's interest in excising Sarek from the story was because he wanted the plot to focus more on the regular characters of TNG and had changed his mind about linking the two Star Trek series together at such an early stage in the series run of TNG, still wanting it to stand on its own. "I didn't see where removing Sarek was going to improve the story, or get me more work with the show," continued Cushman, "so I handed the outline off to Jake Jacobs, who was a writer I'd done some work with in the past." Though Jacobs submitted a revised version of the plot to Roddenberry, neither Sarek nor the story he was to have been featured in were included in TNG Season 2. (Star Trek Magazine Special 2015, p. 75)
Sarek was present in an initial form of the story for third season installment "Yesterday's Enterprise", written by Trent Christopher Ganino and Eric A. Stillwell. Recalled Stillwell, "Gene Roddenberry had circulated a memo saying [...] that Mark Lenard might be interested in making a guest appearance." 
This early version of "Yesterday's Enterprise" began with Sarek arriving at the time planet aboard the Enterprise-D. As a dignitary, he planned to rendezvous with a Vulcan archaeological team that had been using the Guardian of Forever, on the planet, to study ancient Vulcan history at the time of Surak, known as the Time of Awakening. Sarek not only intended to congratulate the archaeologists but also personally escort them back to Vulcan aboard the Enterprise, but before they could leave the planet's surface, the team accidentally altered the timeline so that Surak died before his time. (The Making of Yesterday's Enterprise, pp. 29-31) After being captured as a spy, Sarek convinced a wary Captain Picard – fundamentally altered by the changes in the timeline – to let him travel back in time, via the Guardian, and replace Surak during the Time of the Awakening, in order to restore history. In this way, the story would have accounted for Sarek's name being so similar to the name Surak.
However, Michael Piller vetoed the use of Sarek (as well as the Guardian of Forever) in this instance. (Star Trek: The Next Generation Companion, p. 117) This was because Piller considered the character to be a gimmick from the original series that he'd rather avoid.  Eric A. Stillwell later reflected that Piller rejected the inclusion of Sarek while "telling me he had no interest in doing a story about Spock's father," though this attitude was to ultimately turn out to be "rather ironic." (The Making of Yesterday's Enterprise, p. 34)
At the start of TNG's third season, Michael Piller, taking on the responsibilities of running the show due to Gene Roddenberry's health failing, actually wanted to return Sarek to the story which had been pitched by Marc Cushman. (Star Trek Magazine Special 2015, p. 76) Sarek was reincorporated into the story after the writing staff decided that the guest character in that episode would be a member of Starfleet Command or of the Federation. In order to make the premise fit more easily into the science-fiction genre, someone suggested that a Vulcan experiencing psychological difficulties, due to some form of disease, might have extreme telepathic impact. "From that point it was really short-stepped to, 'What about Sarek?'" remembered Michael Piller. "Sarek is an extraordinarily honorable character who we felt obliged to protect and deal with in a very respectful manner." (Captains' Logs: The Unauthorized Complete Trek Voyages, UK 3rd ed., p. 197) In this case, the use of Sarek maximized the extent to which the story had an impact on and involved the audience. Piller noted, "It brings home the idea that even the greatest of men is subject to mental illness." (Star Trek: The Next Generation Companion, 3rd ed., p. 127) The episode's script, written by Peter S. Beagle without any of the changes Jake Jacobs had made to the story (though his name remained in the screen credits), introduced Sarek with the description, "Sarek is indeed old, but immensely commanding. A genuinely regal figure." (Star Trek Magazine Special 2015, p. 76; )
After the episode "Sarek" was green-lit, the character of Sarek was the subject of a discussion between Marc Cushman and D.C. Fontana when they met. Cushman apologized for having recently "stolen" the character and transferred it to TNG. Though Fontana seemed surprised because she had invented Sarek, she was also polite and gracious about the issue. "She said, 'Well, he belongs to the fans now,'" Cushman relayed. (Star Trek Magazine Special 2015, p. 77)
For Michael Piller and others working on The Next Generation, there were parallels between the ailing Sarek of "Sarek" and Gene Roddenberry at the time of the episode's making, which Piller described as "what I remember most about that episode." He went on to relate the similarities between Roddenberry and the character; "Gene was beginning to go into decline. Not that he was uncommunicative, but it was clear that he was not the same man that he had been. We all respected him so much, and he had been such an important, strong leader of the franchise and everything it stood for. But here is this great man – and I've only known him for less than a year at this point – here is this great man going into decline, and I immediately felt a very strong connection to the premise of 'Sarek' [....] If you go back and look at 'Sarek' closely, what that character is, is Gene Roddenberry." (Star Trek: The Next Generation - The Continuing Mission, p. 119) Piller also noted that this was the intention at the time the episode was written. (Star Trek: The Magazine Volume 3, Issue 8, p. 66)
The makeup for Sarek in the episode of the same name was much as it had been in the previously produced films. "Because Vulcans have an extreme longevity, the years between Sarek's appearance in the motion [pictures] and his first appearance on TNG didn't present us with any problems in designing his makeup," commented TNG Makeup Supervisor Michael Westmore. "We decided not to age him, and the studio agreed, suggesting that we use the natural lines of his face as contours." (Star Trek: Aliens & Artifacts, p. 78)
Leonard Nimoy had been appreciative of how Mark Lenard played Sarek in the episode of the same name as the character, describing this portrayal as "a beautiful performance." (I Am Spock, hardcover ed., p. 325) Likewise, Ronald D. Moore thought the predicament Sarek finds himself in, during the installment which shares the character's name, made for an appealing episode. "Here was a respected, venerated figure in our Trek lore, and he had a problem," Moore observed. "And it wasn't a problem where we were going to give him a hypo and solve it by the show's end." (Star Trek: The Next Generation Magazine, issue 13, p. 24) Moore clarified, "Mark Lenard has a chance to do some solid acting [in 'Sarek']." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 197)
For Sarek's makeup in Star Trek VI, Jerry Quist, a makeup artist from TNG, agreed to join the film's makeup team – since the series was on hiatus while the film was in preproduction – and he alone concentrated on the character's prosthetics for the film. Makeup Supervisor Michael J. Mills recollected, "I just let Jerry take care of that, and he came up with an intermediate look for Sarek – something between what we'd seen in the previous features and what people would be seeing him as on TV." (Cinefex No. 49, p. 45) Also in Star Trek VI, a painting of Ambassador Sarek was hung in the USS Enterprise-A's dining room.
The writing of Sarek's death in "Unification I" was inspired by the fact that, while the episode was being written, the writers were aware that Gene Roddenberry didn't have long to live. (Star Trek: The Magazine Volume 3, Issue 8, p. 66) Ronald D. Moore commented that killing Sarek off took courage and, despite liking the character's final scene, he stated, "It wasn't pretty." (Cinefantastique, Vol. 23, No. 2/3, p. 54) Michael Piller approved of the depiction of Sarek in the "Unification" two-parter overall, enthusing, "I liked the stuff with Sarek, it was very moving." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 233) Concerning Sarek's final canonical appearance, Michael Westmore reflected, "We had to show the effects of the degenerative illness that had afflicted him. We again used the basic design and lines of Mark Lenard's face, but this time we aged him and showed him looking gaunt and drained. We used deeper shadows and placed rubber stretching around his eyes to show fatigue." (Star Trek: Aliens & Artifacts, pp. 78-79) Although Lenard enjoyed his small role in "Unification I" (saying, "It was a bit like King Lear"), he was unaware, during the making of the episode, that it contained a reference to Sarek having died. He explained, after-the-fact, "They only sent me part of the script." (Star Trek - Where No One Has Gone Before, paperback ed., p. 136)
The realization that Sarek had apparently died in "Unification I" came as a sudden shock to Mark Lenard. "I was at a convention somewhere when the episode aired and I was surprised," he reflected. Following the installment's broadcast, Lenard received mail from concerned fans, which he found emotionally moving, but he reckoned he might still reappear. "Jimmy Doohan, who was at that same convention with me, said to me, 'Well, did anybody see him die? Was anybody there?'" Lenard reported. "I said, 'No.' 'Well, then,' he told me, 'you're all right!'" (Star Trek - Where No One Has Gone Before, paperback ed., p. 136)
Ultimately, the role of Sarek was highly important in Mark Lenard's life. Mere months before he died in 1996, Lenard commented, "I suspect that even though I've died on the screen, I will live and die as Sarek of Vulcan. There's no getting away from it anymore." (Star Trek: Communicator issue 137, p. 48)
Despite Sarek making no appearances on Star Trek: Enterprise, the writing staff of that series at one time discussed the possibility of including a young version of the character on the show. (Star Trek Monthly issue 103, p. 18) "We always thought that [...] Sarek was one of the assistants to Soval and that sort of colored his view of the humans," revealed Judith Reeves-Stevens. (Star Trek: The Official Starships Collection, issue 55, p. 17)
Sarek was so integral to the origin story of Star Trek that, in one form, he once again made a movie appearance; his alternate counterpart was featured in the 2009 film Star Trek. (Star Trek Magazine Special 2015, p. 77) Mark Lenard's portrayal of the role provided a basis for Ben Cross' performance in the movie, as the alternate reality Sarek. As such, a sampling of Lenard's presentment of the character was supplied to Cross by Paramount, to prepare Cross for his own take on the character. (Star Trek Magazine issue 145, p. 67) In a deleted scene from the film, showing the aftermath of the birth of Spock, the prime universe version of Sarek was additionally portrayed by Cross; the scene in question takes place before Nero's incursion – dated, on screen, as 2230 (which later became canon in Star Trek Beyond) – thereby making the scene's depiction of Sarek, in fact, "this" character. However, the movie's script described Sarek, in this scene, as being in his "late 40's," rather than sixty-five (which is how old he would be in 2230 if he was born in 2165). The script also established that he deliberately arrives after Spock's birth, he thereafter explaining that Vulcan tradition excludes the father from actual childbirth, despite Amanda Grayson having wanted him to be there.  However, Sarek's absence from Spock's birth is not spoken about in the final version of the scene, leaving the reason for his late arrival unknown. The scene, both as scripted and ultimately edited, showed Sarek as being responsible for naming Spock, taking the name from "one of Vulcan's early society-builders."
The episode "Sarek" stated that Sarek's first wife was from Earth; clearly, this was intended to be a reference to Amanda and that Sarek was not married to the Vulcan princess spoken about in Star Trek V, which admittedly never explicitly says that Sarek ever married the princess, only that she was Sybok's mother.
Mark Lenard was highly impressed with the actresses who were cast to play Sarek's wives. Shortly after appearing in the episode "Sarek", Lenard stated, "As Sarek, I've been graced with my wives so far. They've all been good-looking and charming women." (The Official Star Trek: The Next Generation Magazine, Vol. 14, p. 28)
In "Journey to Babel" and "Sarek", Sarek introduced Amanda Grayson and Perrin respectively as "she who is my wife."
The novel Ishmael gives his full name as "S'chn T'gai Sarek".
In the Thirteenth UK Story Arc, Spock had a cousin named Horek. This implied that Sarek had a sibling, one of Horek's parents.
In the comic story Star Trek: The Next Generation - Perchance to Dream, the crew of the USS Enterprise-D was attacked by a telepathic weapon called the Chova, which forced its victims to experience dreams and hallucinations focused on their personal failures. However, it was discovered that people with multiple personalities could render the Chova inert (since the Chova could only attack one personality at a time). Picard was deliberately infected with the Chova, since his mind-meld with Sarek, the probe that gave him the memories of Kamin, and the remnants of his memories as Locutus of Borg still in his mind all gave him the makings of a multiple personality disorder. The four defeated the Chova, but Locutus then attempted to regain control of Picard's body, nearly 'killing' Kamin and Sarek before Picard gathered the mental strength to stop Locutus.
The novel Avenger revealed Sarek's "Bendii condition" to be actually caused by a poison or special pathogen used by members of the Symmetrists, a Vulcan terrorist group, to murder him without causing suspicion. Spock was also poisoned in this way.
In the novel Engines of Destiny, Sarek became the leader of a resistance fighting the Borg in an alternate timeline where the Borg conquered the Alpha Quadrant during the events of Star Trek: First Contact. However, Sarek retained some memories of the original timeline, which allowed him to recognize Kirk and Scotty when they arrived in 'his' timeline; even having never met them, he knew that he could trust the two of them. In the end, Sarek sacrificed himself to buy time for the temporally-relocated Enterprise-D to return Kirk to the Nexus, as Kirk's presence was required for Picard to survive in order to defeat the Borg's time-traveling experiment.
In the Myriad Universes short story A Less Perfect Union, in which Terra Prime was successful and the Federation-like Interstellar Coalition was formed without an isolationist Earth, Sarek was kidnapped by the Romulans before a conference discussing Earth joining the Coalition, and replaced by Keras (Mark Lenard's Romulan character from "Balance of Terror") – who, being so similar in appearance that this required no cosmetic alterations of any kind, concluded that the two likely shared a common ancestor from before the Vulcan-Romulan schism.