With Star Trek now 50 years old and hundreds of television episodes and 13 films to fill its universe, you're bound to run into celebrity guest stars from time to time. Catch up with sitcom stars, musicians and the occasional theoretical physicist in our list of famous Trek guests.
Scraggly rocker Iggy Pop took a turn on "Star Trek: Deep Space Nine" as an alien Vorta named Yelgrun. He appeared as a villain in heavy makeup in the Western-inspired episode "The Magnificent Ferengi." Pop is know for his solo music, as well as for heading up the punk band The Stooges.
"Cheers" and "Frasier" sitcom star Kelsey Grammer took a turn at the command post of a starship when he played Captain Bateson in the 1992 "Star Trek: The Next Generation" episode "Cause and Effect." Unfortunately for Bateson, he and his crew became stranded in the future.
Australian actor Chris Hemsworth is a global superstar thanks to his role as Thor in the Marvel movie universe. He joined the Star Trek galaxy with the 2009 reboot film "Star Trek" in a small role as Captain Kirk's father, George Kirk. Hemsworth is expected to reprise the role in a fourth reboot film.
Stephen Hawking may be best known as a famous theoretical physicist, but he also has "Star Trek actor" on his resume. Hawking made a cameo appearance in season 6 "Next Generation" episode "The Descent." He appeared in a Holodeck poker game with Albert Einstein, Sir Isaac Newton and Data.
Joan Collins truly launched to stardom in the soapy '80s TV series "Dynasty." Long before her role as a scheming matriarch, she guest-starred on what has often been cited as Star Trek's best episode ever: "The City on the Edge of Forever." Collins played Edith Keeler, a social worker and doomed love interest for Captain Kirk on 1930s Earth.
Whoopi Goldberg was at the height of her Hollywood stardom when she requested and received a recurring guest-star role on "Star Trek: The Next Generation" in 1988. Her character Guinan is a wise, mysterious and ancient alien who runs the Ten Forward lounge on board the Enterprise.
Star Trek fans could smell what The Rock was cooking when the wrestler-turned-actor appeared in the "Star Trek: Voyager" episode "Tsunkatse" in 2000. He battles former Borg Seven of Nine in a space-age version of a fighting pit. Spoiler alert: he wins, but only after giving his famous raised eyebrow to the camera.
"Seinfeld" sitcom star Jason Alexander donned a crazy wig to play the role of the scholar Kurros in the "Star Trek: Voyager" episode "Think Tank."
Ricardo Montalban brought intensity and verve to his role as Khan. He first played the genetically engineered superhuman in the original-series episode "Space Seed" in 1967 and then returned to it for the 1982 film "The Wrath of Khan." The suave actor was perhaps best known for his lead role in "Fantasy Island." And, yes, his impressive chest muscles in "Wrath of Khan" were real.
A "Quantum Leap" sci-fi reunion took place on the Star Trek prequel show "Enterprise" when Dean Stockwell guest-starred next to series regular Scott Bakula, who played the lead role of Captain Archer. "Detained" aired in 2002. Stockwell played Colonel Grat, an officer in charge of a prison on a moon.
This screenshot of Christian Slater is dark because he appears at nighttime on board the Federation ship Excelsior to wake up Captain Sulu. Slater's brief cameo appearance in "Star Trek VI: The Undiscovered Country" came about thanks to his mother. Mary Jo Slater was the casting director for the film.
Kirstie Alley was a relative newcomer when she appeared as Vulcan Starfleet officer Saavik in "Star Trek II: The Wrath of Khan" in 1982. It would end up being her only Trek appearance as she later shot to super sitcom stardom in the late '80s with a lead role in "Cheers."
Wallace Shawn has a long acting resume, but most people know him for his "Inconceivable!" part in the 1987 fantasy movie "The Princess Bride." Fans might not have recognized his face on "Deep Space Nine," but they probably recognized his distinctive voice. Shawn played the recurring role of Ferengi leader The Grand Nagus.
"Back to the Future" isn't the only sci-fi series Christopher Lloyd starred in. Doc Brown himself slathered on a thick layer of Klingon makeup to play Commander Kruge in 1983's "Star Trek III: The Search for Spock."
Christian Slater isn't the only famous face to appear in "Star Trek VI: The Undiscovered Country." Kim Cattrall put on pointy ears to play the role of Vulcan Starfleet officer Valeris. "Undiscovered Country" came out in 1991, years before Cattrall became famous for "Sex and the City."