Sometimes, the Star Trek universe gets weird, and there have been many times throughout the franchise where characters have come face to face with another version of themselves. The idea of doppelgangers has fascinated humanity since ancient times, and storytellers throughout history have crafted stories about strange twins or doubles of people. Ever since split-screen technology became more popular around the 1960s, film and television creators have been finding ways to tell stories about duplicates.

Even with all of the futuristic technology of Star Trek, accidents sometimes happen, and occasionally, those accidents result in duplicate Starfleet officers. Star Trek's first example of a doppelganger comes early in Star Trek: The Original Series, in season 1, episode 5, "The Enemy Within," when Captain James T. Kirk (William Shatner) is split into two separate versions of himself. TOS even created an entire Mirror Universe populated with often cartoonishly evil versions of the characters, and Star Trek has gone back to the doppelganger well often. Whether due to transporter accidents, or time travel shenanigans, or long-lost twins, numerous characters have met their doubles over the years.

10 Captain James T. Kirk - Star Trek: The Original Series

The first doppelganger to appear in the Star Trek franchise was Captain Kirk himself, and he would go on to encounter other versions of himself on multiple occasions. After a transporter malfunction causes Kirk to be split into two distinct halves in Star Trek: The Original Series; "The Enemy Within," he comes face to face with his own worst traits. The evil version of Kirk not only assaults Yeoman Janice Rand (Grace Lee Whitney) but also tries to abandon several Enterprise crew members on the freezing planet Alfa 177. In a later mission to Exo III, Federation scientist Dr. Roger Korby (Michael Strong) creates an android duplicate of Captain Kirk, who also impersonates the real Kirk. In Star Trek VI: The Undiscovered Country, a Chameloid named Martia (Iman) shapeshifts into a version of Kirk, allowing the Captain to fight himself.

9 Lt. Commander Data - Star Trek: The Next Generation

Star Trek: The Next Generation season 1, episode 13, "Datalore" introduces Lore, the evil brother of Lt. Commander Data (both played by Brent Spiner). Both Data and Lore were created by brilliant cyberneticist Dr. Noonian Soong (also Brent Spiner), but Lore quickly proved his malevolence. Upon their first meeting, Data is excited to find that there are others like him until Lore soon reveals his true colors. Lore believes himself to be superior to humanity and to his brother, and he causes problems for Data and the Enterprise on multiple occasions. From stealing the emotion chip meant for Data to allying himself with the Borg, Lore proved to be the opposite of Data in almost every way.

8 Captain Jean-Luc Picard - Star Trek: The Next Generation

When the USS Enterprise-D rescues an adrift shuttle in Star Trek: The Next Generation season 2, episode 13, "Time Squared," they find a duplicate of Captain Jean-Luc Picard on board. As they work to figure out how this could be possible, they discover that Picard's double is from six hours in the future. The duplicate Picard is confused and unable to communicate clearly, and the original Captain Picard is unsettled by the idea that he would ever abandon his crew and ship. In a surprising turn, Captain Picard kills his duplicate when the duplicate attempts to leave the Enterprise. In Star Trek: Nemesis, Picard again encounters another version of himself, but this time it is a younger clone named Shinzon (Tom Hardy) who was created by the Romulans.

7 Commander William Riker - Star Trek: The Next Generation

Another transporter malfunction creates a duplicate of Commander William Riker (Jonathan Frakes) in TNG season 6, episode 24, "Second Chances." When the Enterprise visits the planet Nervala IV, they find a duplicate of Will Riker who has been living alone on the planet for eight years. Riker had been involved in the evacuation of Nervala IV eight years before, and interference from the planet caused the transporter to create a duplicate. One Riker went on to continue his Starfleet career, while the other, who goes by Thomas, was left abandoned on the planet. Will and Thomas immediately clash with one another, and Thomas eventually goes on to take another position within Starfleet. Thomas Riker later makes an appearance on Star Trek: Deep Space Nine after joining the rebel group known as the Maquis.

6 Chief Miles O'Brien - Star Trek: Deep Space Nine

On Star Trek: Deep Space Nine, Chief Miles O'Brien (Colm Meaney) has some of the worst luck of any Star Trek character. Duplicates of O'Brien are created on two separate occasions, but he only interacts with one of his doppelgangers. In DS9 season 3, episode 17, "Visionary," O'Brien begins experiencing visions of the future after being exposed to radiation. After he sees space station Deep Space 9 explode, O'Brien deliberately subjects himself to more radiation so that he can see what caused the explosion. O'Brien then jumps three hours into the future and explains the entire situation to his future self. He then dies of radiation poisoning, leaving the O'Brien from three hours in the future to go back in time and save the station.

5 Captain Kathryn Janeway - Star Trek: Voyager

When the USS Voyager passes through a plasma rift in Star Trek: Voyager season 2, episode 21, "Deadlock," an entire duplicate Voyager is created. Because the antimatter that powers Voyager was not duplicated, the ships begin experiencing power fluctuations. When one Voyager uses proton bursts to gain more power, it causes significant damage to the other Voyager. Eventually, Captain Kathryn Janeway (Kate Mulgrew) travels from her damaged ship to the Voyager which is intact, and the two discuss possible solutions. "Deadlock" is a dark episode, but it's fun watching two Janeways come up with a solution. In the end, the undamaged Voyager is attacked by Vidiians and the Captain Janeway of that ship sacrifices herself and her Voyager to save the other Voyager.

4 The Doctor - Star Trek: Voyager

In Star Trek: Voyager season 6, episode 24, "Life Line," Federation scientists contact the USS Voyager from the Alpha Quadrant and inform them that Dr. Zimmerman (Robert Picardo) is dying. Zimmerman was the creator of Voyager's Emergency Medical Hologram known as the Doctor and he modeled the hologram after his own likeness. When the Doctor learns this news, he requests to be transferred to the Alpha Quadrant via subspace to offer assistance. As the Doctor comes face to face with his creator, he grows frustrated with Zimmerman's attitude towards him. With the help of Lt. Reginald Barclay (Dwight Schultz) and Counselor Deanna Troi (Marina Sirtis), the Doctor and Zimmerman eventually work through their differences and the Doctor saves his creator's life.

3 Spock - Star Trek (2009) & Star Trek Into Darkness

With his Star Trek film released in 2009, J.J. Abrams brought the franchise back to the big screen and introduced an alternate Star Trek reality known as the Kelvin timeline. As a way to connect the Kelvin timeline to the Prime Star Trek timeline, Leonard Nimoy makes an appearance as the now elderly Prime Universe Ambassador Spock. In Star Trek (2009), Ambassador Spock reveals that he and the Romulan Captain Nero (Eric Bana) had been sent back in time and Nero created an alternate timeline by attacking the USS Kelvin. Ambassador Spock encourages the younger Spock (Zachary Quinto) to remain in Starfleet and rely on more than just logic. In Star Trek Into Darkness, Quinto's Spock contacts Ambassador Spock to ask about Khan Noonien Singh (Benedict Cumberbatch), and the elder Spock warns him not to trust Khan.

2 Lt. Brad Boimler - Star Trek: Lower Decks

In a story that mirrors Commander Riker's transporter mishap, Ensign Brad Boimler (Jack Quaid) is cloned in a transporter accident in Star Trek: Lower Decks, season 2, episode 2, "Kayshon, His Eyes Open." In one of Boimler's first adventures on the USS Titan, the Titan comes under attack from the Pakleds. Boimler becomes trapped under debris and as Captain Riker tries to have him beamed out, the transporter creates a duplicate Boimler. The clone Boimler takes the name William and remains on the Titan, while the other Boimler transfers back to the Cerritos. William Boimler is later recruited by the Starfleet Intelligence organization Section 31 after they fake his death. Believing his clone to be dead, Brad Boimler begins to question his own purpose in life, but his friends help him get through it.

1 Captain Christopher Pike - Star Trek: Strange New Worlds

In Star Trek: Strange New Worlds season 1's finale, "A Quality of Mercy," Captain Christopher Pike (Anson Mount) comes face to face with his future self. After Captain Pike tries to avoid his tragic fate, an older Admiral Pike visits him from the future to show him what has changed. The future Pike was never horrifically injured in a delta raty accident, and he remained Captain of the Enterprise. "A Quality of Mercy" revisits the TOS episode "A Balance of Terror," but puts Pike in the place of Captain Kirk. This change in the Star Trek timeline has a domino effect that results in a devastating war with the Romulans and Lt. Spock (Ethan Peck) suffering a terrible injury instead of Pike. After arriving back on his Enterprise, Captain Pike reflects on his experiences and finds himself more prepared to accept his eventual fate.