"If you travel far enough you will eventually meet yourself."
Doppelgänger was a word from the German language which meant an exact duplicate of a living person. The term doppelganger has been used throughout history, most often when someone met an identical copy of themselves who was not a biological twin. Miles O'Brien, Harry Kim, and Naomi Wildman were replaced by doppelgängers of their respective "originals" after they died. (DS9: "Visionary", VOY: "Deadlock")
James T. Kirk
- In 2266, a transporter accident split James T. Kirk into separate "good" and "evil" personas. It was eventually discovered that the two could not live without each other, and they were reintegrated by the transporter. (TOS: "The Enemy Within")
- Later in 2266, Kirk was again duplicated, this time in the form of an android, by Roger Korby and other androids on the planet Exo III. This duplicate was vaporized by Andrea, who mistook it for the real Kirk. (TOS: "What Are Little Girls Made Of?")
- In 2269, a giant clone of Spock was created by Stavos Keniclius 5 and christened Spock 2. When the original Spock departed the planet Phylos, Spock 2 remained behind to work with Keniclius to work on a cure for a plague afflicting the Phylosians. (TAS: "The Infinite Vulcan")
- Stavos Keniclius cloned himself several times in an attempt to find the perfect specimen to create a clone peacekeeping force. (TAS: "The Infinite Vulcan")
- In 2365, the USS Enterprise-D encountered a Jean-Luc Picard from six hours into the future. This Picard was killed by the current Picard, and then vanished. (TNG: "Time Squared")
- In 2366, Picard was replaced by an alien copy; upon returning to the Enterprise-D, the real Picard commented that he "hoped his doppelgänger hadn't caused too much trouble." (TNG: "Allegiance")
- Sometime in the 2360s, the Romulans created a clone of Picard as part of a plot to replace him. This clone, using the name Shinzon, eventually became the Praetor of the Romulan Star Empire before being killed by Picard in 2379. (Star Trek Nemesis)
William T. Riker
- In 2361, a transporter accident on Nervala IV duplicated William T. Riker, stranding one on the surface while the other left with the USS Potemkin. Eight years later in 2369, the Enterprise-D returned to Nervala IV and found and rescued "Thomas Riker". (TNG: "Second Chances")
- In 2365, the Mariposans stole Riker's DNA and created a clone from it. This clone was killed by the original Riker. (TNG: "Up The Long Ladder")
- In 2365, the Mariposans stole Dr. Pulaski's DNA and created a clone from it. This clone was killed by the original Pulaski. (TNG: "Up The Long Ladder")
- Miles O'Brien was killed in 2371, after becoming infected with delta-series radioisotopes following an accident aboard Deep Space 9. He was replaced by his future self from a few hours later, making the current O'Brien a doppelgänger of the "original." (DS9: "Visionary")
- A replicant of O'Brien was created by the Parada government, possibly to assassinate someone at the upcoming peace talks on the station between the government and rebel forces. This O'Brien died never knowing he wasn't the "real" one. (DS9: "Whispers")
- In 2371, the Vidiian Sulan used a genotron to extract B'Elanna Torres' Klingon DNA, leaving her fully Human, and then reconstitute a fully Klingon version of her. The Doctor was able to reintegrate Torres' Klingon DNA into her Human self after her Klingon half was killed escaping the Vidiians. (VOY: "Faces")
- The entire crew of USS Voyager was duplicated by a spatial scission in 2372. The "second" Voyager self-destructed to destroy a Vidiian starship attacking them. (VOY: "Deadlock")
- The "real" Harry Kim was killed on Voyager when he was pulled through a hull breach on deck 15. He was replaced by the other Harry Kim from the "second" Voyager, making the current Harry a doppelgänger of the "first." (VOY: "Deadlock")
- The "real" Naomi Wildman died of complications due to hemocythemia. She was replaced by the "second" Naomi Wildman for the other Voyager, making the current Naomi a doppelgänger of the "first." (VOY: "Deadlock")
- A chameloid impersonated captain James T. Kirk during his imprisonment on Rura Penthe. (Star Trek VI: The Undiscovered Country)
- A coalescent organism was responsible for the duplications and deaths of at least one Starfleet officer and a pet dog. (TNG: "Aquiel")
- Changelings replaced, or impersonated, a number of individuals in the years leading up to, and during, the Dominion War. (Star Trek: Deep Space Nine)
The Silver Blood
- The biomimetic lifeform known as the Silver Blood duplicated the entire USS Voyager crew, and eventually the ship itself. (VOY: "Demon", "Course: Oblivion")
- See Illusory people.
- See: Holographic duplicate.
- See: Mirror universe people.