The very first episode of "Star Trek" aired on Sept. 8, 1966. In the 50 years since then, the series has become one of the most important franchises in Hollywood, spawning six more shows (including "Star Trek: The Animated Series" and the upcoming "Star Trek: Discovery") and 13 films (with a 14th in pre-production). In honor of the 50th anniversary of "Star Trek: The Original Series," Wonderwall.com is taking a look back at 26 celebrities who've popped up in the franchise, starting with Dwayne Johnson. The Rock portrayed a gladiator-like Pendari champion in a 2000 episode of "Star Trek: Voyager." Now keep reading for more!
RELATED: The hottest stars of fall TV shows
A pre-fame Tom Hardy portrayed the main villain -- Shinzon, a Romulan-created clone of Captain Jean-Luc Picard and the leader of the Reman people -- in 2002's "Star Trek: Nemesis."
RELATED: Bad boys of summer TV
In 1993, Kirsten Dunst appeared as Hendril, a child from a telepathic race, on an episode of "Star Trek: The Next Generation."
In 1991, a rising star by the name of Christian Slater portrayed an unnamed red shirt communications officer in "Star Trek VI: The Undiscovered Country."
Ashley Judd made her acting debut as Ensign Robin Lefler on two episodes of "Star Trek: The Next Generation" in 1991.
Iman portrayed the flirtatious criminal shapeshifter Martia, who attempts to kill Captain James T. Kirk and Doctor Leonard McCoy, in 1991's "Star Trek VI: The Undiscovered Country."
Kelsey Grammer portrayed Captain Morgan Bateson, who's stuck in a time loop, on a 1992 episode of "Star Trek: The Next Generation."
Famke Janssen made her television debut in 1992 on "Star Trek: The Next Generation." She portrayed the seductive Kamala, a metamorph who accidentally bonds with Captain Jean-Luc Picard.
In 1988, Teri Hatcher portrayed Lieutenant B. G. Robinson, a transporter operator, on an episode of "Star Trek: The Next Generation."
Kirstie Alley made her feature film debut in 1982's "Star Trek II: The Wrath of Khan." She portrayed the Vulcan Star Fleet Cadet trainee Saavik but was replaced by actress Robin Curtis in "Star Trek III: The Search for Spock" and "Star Trek IV: The Voyage Home."
Adam Scott briefly popped up as the red shirt conn officer of the USS Defiant in 1996's "Star Trek: First Contact." "It's the Enterprise!" his character memorably declares as the starship swoops in to rescue his crew as they're attacked by the Borg.
Tyler Perry portrayed Admiral Richard Barnett, who presided over the Starfleet Academy board tasked with punishing James T. Kirk for cheating on the Kobayashi Maru exam, in 2009's "Star Trek."
Kim Cattrall portrayed Lieutenant Valeris, a Vulcan who was mentored by Captain Spock at Starfleet Academy and was revealed to be a traitor conspiring with the Klingon, in 1991's "Star Trek VI: The Undiscovered Country."
Before he was famous for his work on "Family Guy," Seth MacFarlane portrayed Ensign Rivers, an engineer, on two episodes of "Star Trek: Enterprise" -- first in 2004 and then again in 2005.
"Seinfeld" star Jason Alexander portrayed Kurros, a tactician and the spokesperson for a group of alien scholars, in a 1999 episode of "Star Trek: Voyager."
In 1998, Andy Dick portrayed EMH-2 Dr. Bradley, an emergency medical hologram, on an episode of "Star Trek: Voyager."
Ron Perlman was completely unrecognizable as a Reman in 2002's "Star Trek: Nemesis." He donned heaps of special effects makeup to play Shinzon's second-in-command, the villainous telepath who mentally rapes Deanna Troi.
"Breaking Bad" and "Better Call Saul" star Jonathan Banks appeared on a 1993 episode of "Star Trek: Deep Space Nine."
Before he starred as Doc Brown in "Back to the Future," Christopher Lloyd portrayed the main villain -- the ruthless Klingon Commander Kruge -- in 1984's "Star Trek III: The Search for Spock."
Rage Against the Machine and Audioslave guitarist Tom Morello has just a handful of acting credits on his résumé -- and two are from the "Star Trek" franchise. In 1998, he portrayed a Son'a officer in "Star Trek: Insurrection," and in 2000, he had a brief cameo as Crewman Mitchell on an episode of "Star Trek: Voyager."
"Lost" star Terry O'Quinn portrayed Admiral Erik Pressman, the controversial commander of the USS Pegasus, on a 1994 episode of "Star Trek: The Next Generation."
"X-Men" director Bryan Singer made his acting debut in 2002's "Star Trek: Nemesis." He had a blink-and-you'll-miss-it cameo as an uncredited tactical officer working at the security console on the Enterprise.
In 1998, Iggy Pop portrayed alien Yelgrun on an episode of "Star Trek: Deep Space Nine."
Bill Hader voiced a computer aboard the Vengeance, the vessel belonging to Benedict Cumberbatch's Khan, in 2013's "Star Trek Into Darkness."