Doppelgänger
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, Naomi Wildman, and Kes were replaced by doppelgängers of their respective "originals" after they died. (, )

Physical duplicates

Travis Mayweather 

 In 2152, the automated repair station created a  of Travis Mayweather who was subsequently electrocuted. He was mistaken for Mayweather until Doctor Phlox performed an autopsy. ()

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. ()
 Later in 2266, Kirk was again duplicated, this time in the form of an , by  and other androids on the planet Exo III. This duplicate was vaporized by Andrea, who mistook it for the real Kirk. ()

Spock 
 In 2269, a giant clone of Spock was created by Stavos Keniclius 5 and christened Spock Two. When the original Spock departed the planet Phylos, Spock Two remained behind to work with Keniclius to work on a cure for a plague afflicting the Phylosians. ()

Stavos Keniclius 
 Stavos Keniclius cloned himself several times in an attempt to find the perfect specimen to create a clone peacekeeping force. ()

Jean-Luc Picard 
 In 2365, the  encountered a Jean-Luc Picard from six hours into the future. This Picard was killed by the current Picard, and then vanished. ()
 In 2366, Picard was replaced by an alien replica; upon returning to the Enterprise-D, the real Picard commented that he "hoped his doppelgänger hadn't caused too much trouble." ()
 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. ()
 In 2399, the memories of Jean-Luc Picard were transfered into a golem, shortly before the original's death. This new body was identical apart from a defect in the parietal lobe, which caused Picard's Human body to fail. ()

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 . Eight years later in 2369, the Enterprise-D returned to Nervala IV and found and rescued "Thomas Riker". ()

 In 2365, the Mariposans stole Riker's DNA and created a clone from it. This clone was killed by the original Riker. ()

Katherine Pulaski 
 In 2365, the Mariposans stole Dr. Pulaski's DNA and created a clone from it. This clone was killed by the original Pulaski. ()

Miles O'Brien 
 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." ()
 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. ()

B'Elanna Torres 
 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. ()

USS Voyager 

 The entirety of the  (with the exception of its antimatter supply) was duplicated by a spatial scission in 2372. One of the Voyagers self-destructed to destroy a Vidiian starship attacking them, while the other continued on its way, albeit heavily damaged. ()

Harry Kim 
 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 other Voyager, making the current Harry a doppelgänger of the original. ()

Naomi Wildman 
 Naomi Wildman died of complications due to hemocythemia. She was replaced by the Naomi Wildman for the other Voyager, making the current Naomi a doppelgänger of the original. ()

Kes 
 In 2376, Kes time traveled to 2371, so she could return her with past self to  while Voyager's crew would by handed over to the Vidiians. The attempt failed, and Janeway was forced to kill the older Kes. Her actions warned Janeway of the future, allowing her to prevent the future the older Kes came from. By 2376, when Kes repeated the actions of her deceased counterpart, up to the point of time traveling, Janeway was able to convince her not to time travel, with the "past" Kes opting instead to return to her homeworld. ()

Iliana Ghemor 
()

Shapeshifters

Cellular metamorphosis 
See: Cellular metamorphosis ()

Chameloids 
 A chameloid impersonated captain James T. Kirk during his imprisonment on Rura Penthe. ()

Changelings 
 Changelings replaced, or impersonated, a number of individuals in the years leading up to, and during, the Dominion War. ()

Coalescent organism 
 A coalescent organism was responsible for the duplications and deaths of at least one Starfleet officer and a pet dog. ()

M-113 creature 
 See:  ()

Mimetic simbiots 
 See: Mimetic simbiot ()

The Silver Blood 
 See: Silver Blood.

Vendorians 
 See: Vendorian ()

Illusory 
 See: Illusory people.

Holograms 
 See: Holographic duplicate.

Mirror universe 
 See: Mirror universe people.

External link 
 

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