Over the past 50 years of Star Trek, fans have met tons of new life and new civilizations. And the people portraying some of that new life have occasionally confused the hell out of us.

We know that the franchise is a big deal and has legions of followers, and one of the most obvious signs of its popularity is the surprising guest stars that have featured in the series and movies throughout the past half century. In addition to non-actors, some of the people who have donned masks, prosthetics, or Starfleet uniforms have simply seemed too famous to bother with Voyager or whichever series they ended up on.

Here are 17 of the most surprising guest stars we’ve seen throughout our years of Trek-ing it up.

17. Wil Wheaton’s voice – Star Trek (2009)

Wesley Crusher Wil Wheaton Star Trek The Next Generation TNG Star Trek: The 17 Weirdest Guest Stars Ever

Obviously, Wil Wheaton is no stranger to the Trek, having played widely despised wonder-kid Wesley Crusher throughout seven seasons of The Next Generation. But it was no less surprising when we were in the theater watching director J.J. Abrams’ 2009 remake/reboot/sequel/prequel and thought, “One of those Romulans sounds familiar.”

Wheaton does not physically appear in Star Trek, but he does perform some background voice work on villain Nero’s ship. And just about every scene that takes place there involves some fighting, so you’ll be in the middle of watching all of the stuff explode in space, and then suddenly Wheaton’s voice will emerge from off-screen. It’s a drive-by cameo that is admittedly a pretty cool idea, but it somehow manages to be even more distracting than the non-stop lens flares that Abrams sprinkles across the movie like too much salt.

This one hits the top of the list because it’s more of an Easter egg than anything, but it has such a bizarre execution that we couldn’t help but include it.

16. Stephen Hawking – TNG: ‘Descent, Part 1’

 Star Trek: The 17 Weirdest Guest Stars Ever

The story goes that when theoretical physicist Stephen Hawking received a tour of the Star Trek: The Next Generation studio, he paused by the warp core on the Engineering set and said, “I’m working on that.” And that’s just straight-up delightful.

His cameo in the show’s sixth-season finale, however, had us a little befuddled. He appears as himself (via holographic simulation) as part of a card game that Data is hosting in the holodeck. The other participants are Sir Isaac Newton (John Neville) and Albert Einstein (Jim Norton), because why not? They talk about space-time curvature, and Newton gets all annoyed when his poker buddies question the truth of “the apple story.” Hawking wins the hand with four sevens, and then Data has to go back to work.

The scene makes as much sense as it can, considering it’s two minutes of watching the Physics All-Stars talk trash and gamble. But having Hawking play himself against two actors — especially when one of them is as recognizable as Neville — makes it feel a bit uncanny.

15. Dwayne ‘The Rock’ Johnson – Voyager: ‘Tsunkatse’

 Star Trek: The 17 Weirdest Guest Stars Ever

Dwayne Johnson has shed the “Rock” persona — and professional wrestling — and become an actor in his own right, but he was still The People’s Champion when he showed up on this episode of Voyager, on which he plays a gladiator in an interspecies fighting tournament. And true to the long-held Trek tradition of aliens more or less being humans with some stuff on their heads, Johnson is basically playing The Rock with a puffy, ridged forehead. He even does the thing with the eyebrow and performs his trademark finishing move.

The casting came about because both Voyager and the wrestling show WWF Smackdown were on the same network, and that’s as good a reason as any to cast wrestlers in your sci-fi series. Johnson squares off against Voyager‘s reformed Borg, Seven of Nine, and only when they see their crew mate in danger do spectators Tom Paris, Chakotay, Harry Kim, and Neelix realize that forcing aliens to fight each other for entertainment might be a bad idea. Good hustle, guys.

The Rock wins because he’s The Rock, and Voyager scored its highest ratings of the season. And that’s hardly surprising, because this was also the year that gave us two episodes in which the crew falls in love with a holographic, stereotypical Irish town and another where former crew member Kes returns and starts tearing up the ship with her mind for absolutely no reason.

14. Sarah Silverman – Voyager: ‘Future’s End’

 Star Trek: The 17 Weirdest Guest Stars Ever

Voyager has the highest concentration of weird guest stars in the Trek universe, and while Sarah Silverman is, herself, an actress, it was no less odd to see her show up in the two-part, time-travel episode “Future’s End,” in which she plays a quirky, 1996 scientist and love interest to Tom Paris. And that’s fine.

What was weirder for us was re-watching this episode after having seen Silverman’s comedy and performance in The Aristocrats, which contain jokes that we can’t even describe in vague terms here without giving our site editors aneurysms. Meanwhile, her character on Voyager, Rain Robinson (the ’90s were a very different time), says words like “freakasaurus.”

Honestly, this appearance is only really confusing in retrospect. At the time, we just thought that Silverman was cute and that the contemporary setting looked somehow more alien than all of that stuff happening in space. But it’s kind of a rough time going back, even if this is one of the series’ better episodes.

13. Corbin Bernsen – TNG: ‘Deja Q’

 Star Trek: The 17 Weirdest Guest Stars Ever

We love this Next Generation episode, which has the god-like Q (John de Lancie) stripped of his omnipotence and forced to a mortal life of hunger, cowardice, and facing a universe full of annoyed species who want to kill him.

After the deposed superbeing discovers that he wants to part of this “human” business, he steals a shuttle to save the Enterprise from a sentient cloud of ionized gas with a grudge that will destroy the ship just to get to him. And just when we were getting over our surprise at the selfish jerk doing a good deed, Corbin Bernsen steps through the wall.

He plays another member of the Q Continuum and was, in fact, responsible for “our” Q losing his powers. And he returns them just as quickly to avoid the hassle of having to explain why such a traditionally selfish and childish being would go out so nobly. This episode aired in the middle of Bernsen’s run on NBC’s mega-hit drama L.A. Law, and even as kids watching this episode for the first time, we wondered what he was doing there. And he wasn’t the last famous TV star to “slum it” in the final frontier.

12. Christian Slater – Star Trek VI: The Undiscovered Country

 Star Trek: The 17 Weirdest Guest Stars Ever

Series superfan Christian Slater (Mr. Robot, Gleaming the Cube) has his mother, Star Trek VI casting director Mary Jo Slater, to thank for his walk-on role in the original crew’s final outing. He plays a communications officer on the starship Excelsior who shows up to rouse Captain Sulu (George Takei) to tell him that nobody knows where the Enterprise is.

And that’s it.

His lines originally went to Janice Rand (Grace Lee Whitney), who served on the Enterprise as Kirk’s yeoman on the original series. And she’s still in the movie, but we get Christian Slater for this scene instead, which is probably alright. The movie even builds some suspense around the character, since he starts out silhouetted in the doorway, delivering his report while the audience wonders if that doesn’t sound an awful lot like a person we’re familiar with. And then Sulu turns the lights on, and yep, it’s totally a famous actor wearing a Starfleet uniform.

11. Tom Morello – Star Trek: Insurrection, Voyager: ‘Good Shepherd’

 Star Trek: The 17 Weirdest Guest Stars Ever

Rage Against the Machine co-founder and guitarist Tom Morello has the distinction of sporting two surprising guest spots on Star Trek on his acting resume. He appears as one of the Son’a space raisins in the third Next Generation movie, Insurrection, but you probably can’t even spot him under all those prosthetics.

To make up for all that make-up, Trek steward Rick Berman gave Morello a second bit part on Voyager, and not only can you tell who he is, but he even gets a name and lines. The musician plays Crewman Mitchell, who appears just in time to help Captain Janeway get around her own ship. It’s a cute, charming scene, even if it is a little alarming that the person charged with the safety of Voyager and its crew doesn’t know where Junction Room 16 is.

Our favorite part, however, is how obviously excited Morello is to be on Star Trek. He can barely contain himself.

10. Jason Alexander – Voyager: ‘Think Tank’

 Star Trek: The 17 Weirdest Guest Stars Ever

Jason Alexander’s appearance in the Voyager episode “Think Tank” comes a year after Seinfeld wrapped up, and it was a bit jarring to see him go from co-starring on one of the most popular TV shows ever made to guesting on the second-worst Star Trek series.

His character, Kurros, represents a small group of super-smart beings who go around solving impossible problems in exchange for priceless ore and soup recipes. He offers to help Voyager out of a trap in exchange for a short list of items which includes Seven of Nine. Between this, having to fight The Rock, and several other weird episodes, this show really just wouldn’t leave Seven alone. It isn’t as shady as it sounds, fortunately. Kurros just wants the former Borg to join his group because she knows everything her former Collective does, which is a lot. But it’s also a little dodgy because the Think Tank engineered Voyager’s trouble in order to obtain Seven, and objectifying people is wrong.

This is actually a decent episode, creepy premise aside, and it fulfills Alexander’s dream of appearing as a non-human on Star Trek. Apparently, different series had offered him roles in the past, but the producers patently refused to stick anything on his head.

9. Big Show – Enterprise: ‘Borderland’

 Star Trek: The 17 Weirdest Guest Stars Ever

Our list’s second professional wrestler, Paul ‘Big Show’ Wight, appears on Enterprise as an Orion slave trader. And what that means to non-fans is that he’s a huge, green a-hole.

Orions are famous for three things: being green, selling slaves, and having perpetually semi-nude women whose two favorite activities are dancing and making viewers lose all respect for Star Trek‘s male cast members. The Orions kidnap nine Enterprise crew members, including Vulcan first officer Commander T’Pol, and Big Show takes every opportunity to lift her off the ground and shake her a bit. We don’t know why the wrestler guest stars usually end up physically assaulting the female crew, but they do. Tommy Lister, Jr. (The Fifth Element, No Holds Barred) didn’t when he appeared as a Klingon in the Enterprise pilot, but he was also unconscious most of the time.

Anyway, Big Show auctions off some people and throws some others around, and then T’Pol escapes with the rest of his slaves and kicks him in the junk with her unnatural Vulcan strength, thus ending two of his careers simultaneously.

8. Jane Wiedlin – Star Trek IV: The Voyage Home

 Star Trek: The 17 Weirdest Guest Stars Ever

Star Trek IV: The Voyage Home was a welcome change for the film series when it came out in 1986. It takes a break from space battles and inexplicable Christopher Lloyds to tell a more human story about the Enterprise crew taking a jolly romp to 1980s San Francisco to collect some whales and save Future Earth.

Of course, Future Earth has to be in danger for the humpbacks to be necessary, so the film opens with a mysterious, alien probe beating the snot out of the planet and its defenses with a bunch of noise. It’s scary and chaotic, and — wait, is that one of the Go-Go’s?

Just one year after playing the Singing Telegram Girl in Clue, and three years before she appeared as Joan of Arc in Bill & Ted’s Excellent Adventure, there was the singer-songwriter on a viewscreen. In the middle of everyone at Starfleet Command running around trying not to die, Wiedlin’s character Trillya is issuing a distress signal because their ship is all messed up, and also a deadly virus had escaped and killed 15 crew members.

Just a busy day all around for Starfleet.

7. Joe Piscopo – TNG: ‘The Outrageous Okona’

Joe Piscopo Brent Spiner Star Trek The Next Generation TNG1 Star Trek: The 17 Weirdest Guest Stars Ever

Part of Commander Data’s quest to understand humanity is learning to understand humor, and who better to teach him than the co-star of 1988’s zombie-buddy-cop movie Dead Heat?

Little of the awfulness of this second-season holodeck scene is Piscopo’s fault; it’s an awkward exchange in the middle of an already boring episode. It does turn out that the joke the holographic comic tells Data at “maximum speed” is both racist and homophobic, but at least you don’t pick that up on a regular viewing. You have to go digging for it.

It’s a throwaway scene, and our only reward for it ending is that we get to leave the holodeck and rejoin the “A” plot, which involves the eponymous Okona (Billy Campbell from The Rocketeer) being really “charming.” And it involves something about warring families, an unplanned pregnancy, and lasers, but none of it matters because it’s the second season of The Next Generation, and we’re surprised the show even got out of that hole.

6. Seth MacFarlane – Enterprise: ‘The Forgotten,’ ‘Affliction’

 Star Trek: The 17 Weirdest Guest Stars Ever

Here we have another, Morell0-esque double appearance, this time from Family Guy creator Seth MacFarlane.

In this case, however, he plays the same character, engineer Stewart Rivers, in two episodes. In Season Three’s “The Forgotten,” he makes an error that gets a crewman injured, and Chief Engineer Tucker yells at him. And Season Four’s “Affliction” actually gives him a name and some competence.

MacFarlane has included countless Trek references in his animated series, and several alumni have provided their voices, so it makes sense that he’d at least want to appear on the show. It’s too bad it was Enterprise, but that was all we had at the time.

Rivers serves on both of Starfleet’s warp-5 ships, the Enterprise (registry NX-01) and the Columbia (NX-02). And in his latter post, he totally reports that the dilithium matrix is stable and that the driver controls are configured for warp speed. But that only made it even more confusing because it sounds like Brian Griffin is making the report, and that got our hopes way up.

5. Iggy Pop – Deep Space Nine: ‘The Magnificent Ferengi’

 Star Trek: The 17 Weirdest Guest Stars Ever

“The Magnificent Ferengi” is a weird episode even before rock legend Iggy Pop shows up. It’s about a group of the silly, large-eared aliens staging a rescue mission that goes understandably and ridiculously awry.

Pop plays the episode’s villain, Yelgrun. He is a Vorta, a species with similarly magnificent ears but terrible hair. And they all look a little creepy and weird, so it was actually pretty great casting. Executive producer Ira Steven Behr had wanted to cast Pop on Deep Space Nine for a while, and this episode finally gave him a chance.

This is another time that we hear the character before we see him, and Iggy Pop’s voice is so distinctive and odd that it provides a pretty great build-up. This is a mostly humorous episode, although it does touch a bit on the Ferengi struggling with their species’ reputation as cowards. And Yelgrun has a few dry jokes, but he’s mostly just terrifying and bizarre.

4. Kelsey Grammer – TNG: ‘Cause and Effect’

Kelsey Grammer Morgan Bateson Star Trek The Next Generation TNG Star Trek: The 17 Weirdest Guest Stars Ever

We spend the entirety of “Cause and Effect” watching the Enterprise stuck in a time loop in which it repeatedly crashes into another Federation craft, the Bozeman, and explodes. And by the time the crew figures out how to stop it from happening — good thing they have an android on board — we’re all curious about what is up with that other ship.

The episode ends with the Enterprise finally contacting the other vessel, possibly to exchange insurance information, and it turns out that the crew had been bending fenders with Frasier Crane the entire time.

Yes, Kelsey Grammer plays Captain Morgan Bateson of the Starship Bozeman, a revelation only made more surprising by the fact that Grammar was also appearing in the final season of Cheers when this episode first aired. Unlike Jason Alexander, Grammer’s mega-show was still on, and his next big hit, Frasier, was still ahead of him. So while it was surprising to see this actor pop up on the main viewer, we can’t really blame him.

He was, after all, just under halfway through his 20-year stint playing the same role.

3. Bryan Singer – Star Trek: Nemesis

Star Trek Nemesis Bryan Singer Cameo Star Trek: The 17 Weirdest Guest Stars Ever

In the middle of the Enterprise’s climactic battle against Picard’s evil clone, Shinzon (Tom Hardy), Commander Worf’s tactical console makes that noise that means something bad is happening. In fact, an enemy boarding party has just appeared on the ship, so Worf, Commander Riker, and their expendable team head off to take care of that. Worf nods to someone off-screen to take over his post, and that unnamed lieutenant happens to be X-Men director Bryan Singer.

Well, Bryan Singer plays him, anyway. We don’t know that it’s actually Bryan Singer, but if Stephen Hawking can play himself in the 24th century, we don’t see why the guy who made Apt Pupil can’t. Star Trek is just full-up with time travel, you know.

Regardless, the acclaimed director appears on screen for roughly two seconds before the cinematographer relegates him to background work and/or a similar-looking extra. We actually timed it: It’s less than two seconds. You could not blink and still miss that Bryan Singer was in the 10th Star Trek movie, and you’d still have seen more confusing things happen in the story.

2. King Abdullah II bin al-Hussein – Voyager: ‘Investigations’

 Star Trek: The 17 Weirdest Guest Stars Ever

We don’t know how many people reading this would recognize the king of Jordan if they saw him, but he was totally in an episode of Voyager.

He was “only” a prince when he made his cameo, however, because that’s the sort of crazy stuff that princes do before they have to run entire countries. The prince doesn’t have any lines, but you see him a few minutes in hanging out with Ensign Kim before Neelix shows up to interrupt the conversation that the Screen Actors Guild wouldn’t even allow them to have in the first place.

King Abdullah II appears for under 10 seconds, but the scene is blocked and performed in such a way that even if you don’t realize that the guy in the blue uniform is the future King of Jordan, you feel like they must have put him in there for some reason. Abdullah II’s U.S. advisor arranged the appearance under the guise of a set visit, and the monarch is such a big fan that he’s helped arrange a Trek-themed area in the on-again, off-again Red Sea Astrarium resort in Aqaba.

1. Mick Fleetwood – TNG: ‘Manhunt’

Antedeans Star Trek The Next Generation TNG Star Trek: The 17 Weirdest Guest Stars Ever

Like King Abdullah II, Mick Fleetwood was allowed to appear in a Star Trek episode — in this case, The Next Generation‘s “Manhunt” — but SAG rules declared that he couldn’t say anything. And that only makes his appearance tougher to spot, because you definitely aren’t going to recognize his face.

Fleetwood plays an Antedean who starts off catatonic and ends up scarfing down a barrel of space sardines with his colleagues. They are tall, nightmarish aquatic folk, and they are also planning to blow up the conference they were there to attend. But luckily, psychic Lwaxana Troi arrives to spoil their plot, and all the denials in the galaxy can’t get the fish-people off the hook or out of the cooler.

The Fleetwood Mac drummer was annoyed at having to lose his beard to go full-on gill-man, but he made a deal that got him a scene where he goes through the transporter, and that apparently made the shave worthwhile. We’re going to go ahead and assume that Fleetwood knew that the transporter didn’t actually work when he made that deal. Regardless, this is a cameo that is absolutely impossible to see unless you were on-set or know Mick Fleetwood, and it’s definitely the most out-of-left-field guest spot in the franchise’s 50 years.

Did we miss your favorite out-of-place Trek cameo? Let us know in the comments.

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