First airing in 1966, Star Trek, better known as Star Trek: The Original Series or TOS nowadays, introduced audiences to a diverse cast of both alien and non-alien characters. These characters had a lasting effect on fans and their popularity is still prevalent within the Star Trek community. With the original series' success, subsequent spin-off or sequel Star Trek shows were created, where many actors from the original series guest-starred on.

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Some of these actors reprised their original roles from the original series, re-introducing a once-beloved character to the current Star Trek mythos, while others played new characters, further expanding the Star Trek universe.

8 Grace Lee Whitney appeared as Janice Rand in the original series, three of the Star Trek original series films, & in one episode of Star Trek: Voyager

Grace Lee Whitney as Janice Rand, Yeoman and Comms Officer, in Voyager and TOS

Whitney played Janice Rand, a Starfleet officer aboard the Enterprise. She was assigned as Kirk's yeoman, a personal assistant of sorts. She appeared in eight episodes of TOS: "The Corbomite Maneuver," "The Enemy Within," "The Man Trap," "The Naked Time," "Charlie X," "Balance of Terror," "Miri," and "The Conscience of the King."

The character gets promoted to Chief Petty Officer and transporter chief in Star Trek: The Motion Picture and was a communications officer in Star Trek IV: The Voyage Home and in Star Trek VI: The Undiscovered Country. In "Flashback" from Star Trek: Voyager, Whitney guest stars as Janice Rand, who is now aboard the Excelsior, captained by Sulu.

7 Majel Barrett Roddenberry was one of the few actors to have had a role in TOS, the TOS Films, the animated series, TNG, DS9, Voyager, & Enterprise

Majel Barrett as Christine Chapel in TOS, Lwaxana Troi in TNG and DS9, and an animated alien

Majel Barrett Roddenberry, as the name suggests, was Gene Roddenberry's second wife. And as expected, she was greatly involved in the Star Trek universe. She first appeared as nurse, and later doctor, Christine Chapel in 25 episodes of TOS and later in Star Trek: The Motion Picture and Star Trek IV: The Voyage Home. She perhaps is better known for playing Lwaxana Troi, the Betazoid mother of Deanna Troi, in TNG and DS9.

Besides her live-action portrayals, Barrett also voiced the federation ship computer in TOS, the animated series (along with other minor characters), TNG, Ds9, Voyager, Enterprise, and in the various movies (including the first Abrams reboot movie).

6 William Shatner was a regular for the animated series and also played Kirk in 7 of the Star Trek films

Kirk talking with Picard in Generations

William Shatner reprised his role as the iconic Captain James T. Kirk in animated series, along with most of the original cast from TOS. He appeared in every episode besides "The Slaver Weapon."

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He would also play Kirk in 7 of the Star Trek films: The Motion Picture, The Wrath of Kahn, The Search For Spock, The Voyage Home, The Final Frontier, The Undiscovered Country, and finally in Generations. Kirk dies in Generations so the character does not make an appearance in any of the later Star Trek shows.

5 Nichelle Nichols portrayed Nyota Uhura in the animated series & in 6 of TOS films

Nichelle Nichols as Uhura in the TOS films and animated show

Nichelle Nichols was able to reprise her role as Nyota Uhura, the Enterprise's secretary, in the animated series and in the first 6 TOS films. She starred as Uhura in 16 episodes of the animated series; Nichols also voiced various other minor characters, mostly aliens, on the animated show.

The character Uhura played a much bigger role in the animated series than in TOS, something that both annoyed and relieved Nichols.

4 George Takei reprised his role as Hikaru Sulu in the animated series, 6 of the TOS films, & in one episode of Voyager

Helmsman and Captain Sulu in TOS, Voyager, and Animated Series

George Takei played senior helmsman Hikaru Sulu in 19 episodes of the animated series, two where he had no lines, and in the first six TOS films. His more notable appearance however was as a guest star in the Voyager episode "Flashback."

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In the episode, a newly promoted Captain Sulu goes on a prohibited rescue mission for Kirk and McCoy; he is the captain of the USS Excelsior and Tuvok is one of his junior science officers.

3 DeForest Kelley was a regular on the animated series as Dr. Leonard McCoy & made a special guest appearance in TNG

McCoy taking a tour of the newly commissioned Enterprise D

Similar to George Takei, DeForest Kelley was a regular in the animated series and played Dr. Leonard McCoy in 19 episodes. Additionally, he was also McCoy in the first six TOS films.

Kelley is once again McCoy in the first TNG episode "Encounter at Farpoint." In the episode, audiences see a now considerably old Admiral McCoy taking a tour of the newly commissioned Enterprise-D with Data. He tells Data to take care of the ship and in return, the ship will bring the crew home safely.

2 James Doohan appeared in TOS, the animated series, 7 of the Star Trek films, & was a special guest star in a TNG episode

Scotty talking to Picard on a replica Enterprise

James Doohan, better known as Montgomery "Scotty" Scott to Trekkies, was a series regular in TOS and in the animated series where he was in every episode except for "The Slaver Weapon." He also appeared in the first 6 TOS films in addition to Generations.

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In TNG, Doohan returned and guest-starred as Scotty in the episode "Relics." In "Relics" the TNG crew rescue Captain Montgomery Scott from a starship crash, to which he is the only survivor. The episode mainly deals with him re-adjusting to life in the 24th century.

1 Leonard Nimoy reprised his role as Spock in the animated series, 6 of the TOS films, TNG, & in two of the J.J. Abrams reboots

Spock as a science officer and then as an ambassador

Spock is perhaps the most beloved and well-known character in the Star Trek universe. Because of this, Leonard Nimoy as Spock has appeared on many of the various Star Trek shows and films throughout the years. Aside from TOS, Nimoy played Spock in every episode of the animated series, 6 of the original TOS films, TNG, and in Star Trek and Star Trek Into Darkness (the Abrams' films).

Nimoy truly elevated the character, cementing Spock's importance in the Star Trek universe. Without him, the entire Star Trek universe would not have been as connected nor as spectacular as it is.

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