Now: Chris Pine
He dabbled in TV with bits on ER and Six Feet Under before going the romantic comedy route on the big screen opposite Anne Hathaway in The Princess Diaries 2: Royal Engagement. His way with the ladies might help him nail the cocky, womanizing confidence of the good captain.
Then: William Shatner
Shatner has done a bit of everything, including writing, making music and producing. But he didn't lose his boob-tube presence. Shatner recently wrapped a six-year, multiple Emmy-winning run as Denny Crane on ABC legal drama Boston Legal. And who can forget his most important role yet — that of pitchman for cheap airfare as "Priceline Negotiator"?
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Now: Zachary Quinto
He's turned in work on CSI and 24, but the furry-browed actor is best known for his role as skull-splitting, shape-shffting serial killer Sylar on Heroes.
Then: Leonard Nimoy
Since his days on the Enterprise ended, Nimoy has popped up doing voice-over work on projects such as A&E's Ancient Mysteries and appearances on Futurama and The Simpsons. He most recently appeared in Star Trek director J.J. Abrams' Fox series Fringe as William Bell, the mysterious former partner of Walter Bishop. He will also reprise his role as Spock in the Trek reboot.
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Dr. Leonard "Bones" McCoy
Now: Karl Urban
This New Zealand-born actor is no stranger to fantasy. He's best known for playing Eomer in the second and third installments of the Lord of the Rings trilogy and his role in the Viking adventure Pathfinder. He also played a Russian assassin in The Bourne Supremacy and starred in the big-screen adaptation of the computer game Doom.
Then: DeForest Kelley Kelley never got out from under his role on Star Trek, and despite a few other TV and movie gigs, basically went into retirement. He did take up poetry, and published two books of his work before dying of stomach cancer in 1999.
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Now: Zoe Saldana She got her start on an episode of Law & Order in 1999, but soon landed in features such as Center Stage, Britney Spears' Crossroads and Drumline. She is probably best known for her small role as pirate Anamaria in Pirates of the Caribbean: The Curse of the Black Pearl and her part as an airport employee in The Terminal.
Then: Nichelle Nichols Post-Star Trek, Nichols has volunteered for NASA and has also appeared in animated series Futurama and The Simpsons. Most recently, she guested in a Season 2 arc of Heroes as Nana Dawson, the matriarch of a New Orleans family who cares for her orphaned granddaughter and great-nephew, both of whom have abilities.
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Now: Anton Yelchin
This Russian-born youngster made his big-screen debut in 2001, appearing in films such as Along Came a Spider and Hearts in Atlantis. He's also appeared in the Showtime drama Huff and Alpha Dog. He'll hit the big screen again later this summer in Terminator: Salvation.
Then: Walter Koenig
He reprised his role of Chekov for the fan webseries Star Trek: New Voyages and the independent film Star Trek: Of Gods and Men, both in 2006. He also appeared in a 12-episode arc of Babylon 5 and visited refugee camps along the Burma-Thailand border in July 2007 as part of a humanitarian effort.
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Now: John Cho
Though he's made pit stops on the TV series Grey's Anatomy, House, and How I Met Your Mother, he is best known for his roles in raunchy comedy film franchise American Pie and the two Harold and Kumar flicks.
Then: George Takei
Takei has made multiple TV appearances since his days on the Enterprise, with the most notable being his role as Hiro Nakamura's father on Heroes. He also serves as the announcer for The Howard Stern Show on Sirius radio and appeared on the U.K. version of I'm A Celebrity... Get Me Out of Here!. He came out in 2005, and in September 2008, Takei married his longtime partner Brad Altman.
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Montgomery "Scotty" Scott
Now: Simon Pegg
The British funnyman starred in the BBC series Spaced and the zombie- and buddy cop-spoofing films Shaun of the Dead and Hot Fuzz. He also teamed up with Friends star David Schwimmer for Run Fat Boy Run and most recently appeared in How to Lose Friends and Alienate People.
Then: James Doohan
Also a victim of typecasting, Doohan stuck mostly to making personal appearances and cameos in films and TV shows that poked fun at himself and his Trek character. He suffered from Parkinson's disease, diabetes mellitus, and pulmonary fibrosis in later life and was diagnosed in 2004 with Alzheimer's disease. He died in 2005.