Marvel and DC. Pepsi and Coke. Ash and Gary. All of these are legendary rivalries going back decades. But none of them reach the level of one of the biggest: Star Wars and Star Trek. Two science fiction series with weird aliens, spaceships, and laser guns, Star Wars and Star Trek fans have been battling it out since Star Wars premiered in 1977. A lot of fans may think J.J. Abrams was the first to jump the gap, from his Star Trek in 2009 to The Force Awakens in 2015.

But these series have been running for decades in multiple mediums. Star Trek obviously had the multiple TV shows, but there's also the long series of movies bringing in new talent. And for Star Wars, there's the legendary Expanded Universe, spanning television, radio, everything the mind can imagine. And since Hollywood is a lot smaller than one might think, a lot of actors have appeared in both Star Wars and Star Trek, well before Abrams touched either series. Actors from every series of Trek have appeared in one Star Wars piece or another, and even, horror of horrors, a few main cast members have lent their talents to the Wars. Some are better known for Trek, others for Wars, and some you might be surprised to find out were in both.

15 GREG GRUNBERG

Best known for the television show Heroes, a lot of Greg Grunberg's success can be attributed to his friend, J.J. Abrams. Catching his big break in Abrams' directorial debut Felicity, he would go on to appear in cult classic Alias and then Lost, playing the pilot who was at the helm of the fateful plane crash.

Several years later, when Abrams began working on Star Trek, Grunberg would return once again to play an engineer named Olson. Although he had to step out of the film due to scheduling conflicts, he was able to overdub James Kirk's uncle. He would later appear in person in Star Trek Beyond, but by then he had already appeared in The Force Awakens as Resistance pilot Snap Wexley. The character was mysteriously absent from The Last Jedi, however.

14 SIMON PEGG

Probably the most well-known crossover on this list, Simon Pegg is yet another J.J. Abrams convert. First appearing as Chief Engineer Scotty in Abrams' two Star Trek reboots, Star Trek in 2009 and Into Darkness in 2013, he would make the jump with Abrams to The Force Awakens, playing Jakku junkmonger Unkar Platt.

Less known is his voice appearing in The Clone Wars as bounty hunter Dengar. There's also his often unspoken contribution to The Force Awakens, convincing Abrams to rely more on practical effects over CGI, crediting his daughter's delight upon seeing puppet Yoda in The Empire Strike Back. So there you go, you have Simon Pegg to thank for puppet Yoda in The Last Jedi. The jury remains out on who to blame for the weird CGI filter, though.

13 BRIAN GEORGE

Most known for his role on Seinfeld as restaurateur Babu Bhatt, Brian George first appeared in Star Trek in an episode of Deep Space Nine, playing Dr. Julian Bashir's embarrassing father. There, he revealed Julian's big secret: he was genetically engineered. He would later appear in a smaller role in Voyager as Ambassador O'Zaal, running an interstellar race entered by Tom Paris.

His contribution to Star Wars would be significantly larger, playing Old Republic Jedi Master Ki-Adi-Mundi in The Clone Wars. A prolific voice actor, George had appeared previously in hundreds of series, most notably Avatar: The Last Airbender, Spectacular Spider-man, Superman: The Animated Series, and Kim Possible. George currently appears in The Big Bang Theory and The Expanse, putting his hard won nerd cred (and immense talent) to good use.

12 DEEP ROY

A prolific actor with a career going back decades, fans will most likely recognize Deep Roy as the face of the Oompa Loompas in Tim Burton's ill-advised Charlie and the Chocolate Factory. But well before that, Roy would appear as an uncredited double for Yoda in The Empire Strikes Back, and more notably as Droopy McCool of the Max Rebo Band in Return of the Jedi.

He made the jump to Star Trek well down the line, with J.J. Abrams' 2009 reboot. Playing Simon Pegg's alien sidekick Keenser, he would go on to appear more regularly in the rest of the series. Most notably, Roy is the only actor ever to have appeared in Star Trek, Star Wars and Doctor Who, where he played Mr. Sin in a six-part story during Tom Baker's time as the Fourth Doctor.

11 CLIVE REVILL

A talented stage actor and prolific voice actor with a career spanning more than 50 years, Clive Revill has probably appeared in at least one thing you really like (besides Star Trek and Star Wars). Perhaps best known for providing the voice of Alfred Pennyworth in Batman: The Animated Series, his Star Trek appearance was a bit less impressive. Playing a version of English character Sir Guy of Gisbourne, he hounded the crew in a somewhat bizarre time travel plot.

11 years earlier, he had provided the voice for an iconic Star Wars character. In The Empire Strikes Back, Emperor Palpatine made his first appearance, played by an old woman with chimp eyes superimposed over her own, with a voice provided by Revill. While Revill was cut out of the film and replaced by Ian McDiarmid in the 2004 DVD re-release, he would go on to provide the voice for several non-player characters in the 2011 video game Star Wars: The Old Republic.

10 JASON WINGREEN

Another victim of the DVD release, Jason Wingreen provided the voice for legendary bounty hunter Boba Fett in The Empire Strikes Back. His voice would end up replaced with Temuera Morrison in the re-release, much like Clive Revill, in the service of better continuity with the prequels.

While most know him for his role as Harry Snowden in All in the Family and its spinoff Archie Bunker's Place, Star Trek fans will recognize him from the Original Series episode "The Empath," playing Federation scientist Doctor Linke. While he might be remembered a bit better for Star Trek than Star Wars, the reverse holds true for his personal experience, saying, "Star Trek has never been in my life the way Star Wars was. Star Wars really changed things for me. But Star Trek, I remember, was not an audition. My agent submitted my name and I was given the job. I have no real memory of shooting the episode. I'm sorry about that."

9 PATTY MALONEY

Time for a real deep pull. Best known for her episode of Star Trek Voyager, Patty Maloney played "the little woman" in "The Thaw." There, as one of the Clown's many creations, she spoke first to the crew of the Voyager after they landed on her planet to investigate odd weather patterns.

She mostly played bit parts for much of her career, but her connection to Star Wars is, perhaps fortunately, lost to time. Much has been said about the infamous Holiday Special, most of it bad. But Patty, who played Chewbacca's son Lumpy (short for Lumpawaroo), was happier with the film than most people involved probably are. "We were all very pleased with the outcome of it," Maloney said of the movie before quickly correcting herself: "Actually… I was. I was very pleased with it."

8 CLANCY BROWN

An immensely prolific voice actor, you have probably heard Clancy Brown's voice in something today. From Lex Luthor in Superman: The Animated Series, to the Kurgan in Highlander, to his possibly most famous role Mr. Krabs in Spongebob Squarepants, Brown has appeared in pretty much every nerd-related media from the past 30-odd years. Star Trek and Star Wars are no exception, of course.

He first appeared in the Enterprise episode "Desert Crossing," playing Zobral as Archer and Tucker find themselves caught in a war between his house and a rival. His contribution to Star Wars would be considerably larger, lending his immediately recognizable voice to The Clone Wars as Savage Oppress, brother to Darth Maul. While Savage would die with The Clone Wars, Brown would return to Star Wars to voice Lothal governor Ryder Azadi in Rebels.

7 SAM WITWER

A huge Star Trek fan as a kid, Sam Witwer was thrilled to finally make a cameo in Enterprise as a Xindi-Arboreal. Better known for his roles in Smallville, Battlestar Galactica, and Being Human, his contributions to Star Wars surprisingly far outweigh his contributions to Star Trek. Most immediately recognizable for video game fans as the face (and voice) of Starkiller in The Force Unleashed, he would go on to provide the voice for Emperor Palpatine in Rebels and various video games, as well as background voices in The Force Awakens and Rogue One.

His biggest role, however, is the voice of Darth Maul in The Clone Wars and Rebels. Portraying the character from crazed cyborg through a surprisingly complex character arc, he would finally lay the character to rest in a rather touching moment with Obi-Wan in Rebels.

6 RON PERLMAN

Ron Perlman has made his rounds in the nerd pantheon, playing Hellboy, appearing in Pacific Rim, and voicing the Lich in Adventure Time. Not one to turn down a role, Perlman has appeared in a staggering 237 projects. Buried somewhere in there are Star Trek and Star Wars, or else why would he be on this list?

His first appearance is in 2002's much-maligned Star Trek: Nemesis as Shinzon's main henchman, the Reman viceroy. He meets his fate in a battle against Riker on a catwalk, that classic Star Trek battleground. His turn in Star Wars was a bit better received, if more minor. There, he provided the voice for Trandoshan scavenger Gha Nackt in The Clone Wars. He also met an unfortunate end trying to swindle General Grievous, who responded with a lightsaber through the chest.

5 IAN ABERCROMBIE

Ian Abercrombie is no stranger to science fiction, making appearances in the original Battlestar Galactica and Babylon 5. His turn in Star Trek didn't come until 1999 in Voyager, appearing in two episodes. The first, a Kadi minister in "Someone to Watch Over Me," and the second, an Irish drunk two years in "Spirit Folk."

As with most members of this exclusive cohort, Abercrombie entered the Star Wars universe with The Clone Wars. There, he voiced future Emperor Palpatine, delivering some of the most memorable performances in the series until his death in 2008. Although he was replaced by legendary actor Tim Curry, Curry found Abercrombie a tough act to follow, with fans voting nearly unanimously in favor of Abercrombie when asked who did a better job.

4 OLIVIA D'ABO

Another fan blessed with a part, Olivia D'Abo appeared in The Next Generation as Starfleet intern Amanda Rogers in the episode "True Q." Eager to prove herself and win a position in Starfleet, her ambitions are shattered when Q reveals that she too is a Q. After her turn in Trek, she would go on to do extensive voice work, appearing the DC Animated Universe as Star Sapphire and Morgaine Le Fay, and Invader Zim as Tak.

Following the trend, she would later join the ranks of Star Wars/Star Trek crossovers through The Clone Wars, voicing Old Republic Jedi Master Luminara Unduli. Unduli would appear throughout the series, but like many of the rest of the Jedi, she would meet her fate in Order 66.

3 GEORGE COE

One of the founding cast members of Saturday Night Live, George Coe was a fairly prolific film and television actor. Most fans will recognize Coe from the memorable filibuster episode of The West Wing, but before that, he played a part in The Next Generation episode "First Contact," not to be confused with the movie of the same name. In the episode, he negotiates with Picard over whether his civilization is ready for warp travel, ultimately deciding against it.

Making the jump to Star Wars in, you guessed it, The Clone Wars, he played alien Tee Watt Kaa in a similar role to his Star Trek appearance. He would later lend his voice to Star Wars: The Old Republic, and continue his voice work until the end of his life as Woodhouse in Archer.

2 BRENT SPINER

Yes, that's right, even a main cast member made the jump. Brent Spiner is, obviously, most famous for playing Data in The Next Generation. He also played Data's "brother" Lore and his "father" Dr. Noonien Soong, once playing all three at the same time. He also played a less-developed Data in the form of android B-4 in Star Trek: Nemesis, and an ancestor of Soong, Erik, in Enterprise.

Breaking the mold, Spiner first appeared in Star Wars not in The Clone Wars, but in its sequel series Rebels. There, he played exiled Senator Gall Trayvis. The treacherous senator would only appear in one episode, but it remains one of the more memorable Rebels episodes. While Spiner grew dissatisfied with Star Trek as the years passed, his move to Star Wars showed he was quite willing to break with his most famous role to join a rival series.

1 GEORGE TAKEI

What's this? Not just an main cast member but an original main cast member? Most famous for his work in The Original Series as Sulu, Takei would appear in 52 episodes and six movies. He would also reprise the role in the animated series, and even in Voyager, finally promoted to Captain. After Star Trek, his talents turned more towards voice work, appearing in Kim Possible, Kung Fu Panda, and perhaps most memorably, Mulan. He would also make a memorable recurring appearance in Heroes.

Once again, the lure of The Clone Wars brought a Star Trek actor to Star Wars. As Neimoidian General Lok Durd of the Seperatists, Takei played an arms developer responsible for several superweapons. Although he was planned to be a recurring villain, scheduling conflicts resulted in him only appearing in one episode. Despite being a Trek loyalist through and through, Takei didn't view his Star Wars role as jumping ship, as espoused in our very own interview.