(Sorry, Idris Elba- and Kirstie Alley-sized lead parts, in Star Trek Beyond and Star Trek II: The Wrath of Khan, respectively, or a regularly recurring, Whoopi Goldberg-esque gig were not considered. We're talking guest-star roles only.)
Click ahead for a look at the jaw-droppers: the Star Trek guest stars who made us sit up and go, "Wait, what are they doing here?!"
(Disclosure: TV Guide is owned by CBS Interactive, a division of ViacomCBS.)
Best known as the blue-hued Mystique from the X-Men movies, Romijn showed the right stuff -- and a new brunette 'do -- as Number One during a throwback story arc on Discovery.
In 2000, the future Fast & Furious star was the pro wrestler known as The Rock when savvy Voyager producers cast him as a pugilistic Pendari, and put him in the ring with Seven of Nine (Jeri Ryan).
The opening minutes of J.J Abrams' Star Trek reboot feature a glimpse of the clean-cut, pre-Thor Hemsworth as James T. Kirk's doomed but good-looking father, George Kirk.
It's a bit hard to tell, what with all the sweat, tears and laboring going on in this film's tragic opening sequence, but James T. Kirk's mother is played by Morrison, the future star of Once Upon a Time and This Is Us.
Perry, best known as the man behind the Madea character and media empire, said he was "shocked" that director J.J. Abrams asked him to play the Kirk-scolding Admiral Richard Barnett.
So much of Ryder's work in the J.J. Abrams film was cut (and relegated to the extras disc) that it may not be until the closing credits that you learn, to your amazement, that the then-37-year-old played Spock's mom.
You cannot see the Saturday Night Live alum in this 2013 film, but you can hear him as the calm, collected voice of the out-of-control U.S.S. Vengeance's computer system.
In this 1993 episode, if you look past the Cairn ear wings, you can see the 11-year-old Dunst before she became a star via Interview With the Vampire and the Tobey Maguire Spider-Man movies.
In 1991, it was jarring to see Slater, already a big star, emerge from the shadows of the Excelsior to stir a sleeping Captain Sulu in Star Trek: VI: The Undiscovered Country. More than a quarter-century later, to be honest, it's still jarring.
In 1991, Judd was best known, if at all, as Wynonna Judd's baby sister and Naomi Judd's other daughter when she snagged a minor role as Ensign Robin Lefler. She shared her first on-screen kiss with Wil Wheaton's Wesley Crusher.
As there's no escaping Amazon, there's no escaping Amazon's CEO (pictured right), who, per TheWrap, "appears early on in the  film attaching a universal translator" to another alien (played by Lydia Wilson, pictured left).
Family Ties' Andy Keaton disappeared into Klingon makeup for seven Next Generation episodes as Worf's son, Alexander Rozhenko, from 1992 to 1994.
This 1992 appearance by Janssen, as the empath Kamala, is one of her earliest works as an actress. The former model was still years away from the James Bondand X-Men franchises.
In this 1992 episode about a time loop, nothing is more disorienting than the sight of Grammer on the Enterprise view screen as U.S.S. Bozeman Capt. Morgan Bateson. (All together now: Hey, it's Frasier!)
The future alt-comic icon not only non-ironically played a Los Angeles astronomer on this time-traveling, 1996 two-parter, but she was so endearing that she almost got a full-time job out of the deal.
In a way, this is the least surprising Trek cameo: The sci-fi franchise and the author of A Brief History of Time were made for each other. Still, it's a kick to see the real Hawking play poker with fictionalized versions of Albert Einstein and Isaac Newton.
Four years after Tank Girl seemed to stall a thriving film career (Point Break, A League of Their Own), Petty appeared out of nowhere for this 1999 episode as the scavenger Noss. The actress went on to star in Netflix's Orange Is the New Black.
If you told the people of 1968 that the Stooges' frontman would appear on a 1998 Trekspinoff coolly playing a Vorta and negotiating a prisoner swap, they would've asked you what you were smoking (and where they could get some).
One minute you're enjoying this 1991 movie, the next you're enjoying the unexpected thrill of seeing the model-actress play games with Kirk (William Shatner) and Bones (DeForest Kelley) as the shape-shifting Martia.
Late in this 2013 film, look for a split-second, transporter-room reaction shot from an alien crew member. That alien crew member, named Moto, is played by the Nightmare on Elm Street actress turned special-effects makeup guru.
Christopher Lloyd (pictured center) was easy to spot in this 1984 movie as the main Klingon villain, Kruge. But Larroquette, who was just beginning his Night Court run, was impossible to I.D. as the underling, Maltz. (Hint: He's the one on the left.)
Decades before he was on Justified, Arrow, Suits and more, this now-familiar face was a novice in this 1996 movie. His Enterprise helmsman Lt. Hawk was a classic "redshirt": The character didn't make it out of the movie alive.
The future Emmy-winner (for Lost) appeared in a 1994 Next Generation episode as Riker's old boss.
In this 1993 episode, there's a reason the monosyllabic Klingon, Koral, is very tall: His portrayer is the 6-foot-9 basketball great, who at the time was an active player for the Los Angeles Lakers.
Director Justin Lin knew the Community star was so unrecognizable in his 2016 film as the alien Fi'Ja, that Lin posted a picture on his Website, and asked readers to guess who the famous fellow on the left was.
In this 2002 film, the X-Men director turns up as on the Enterprise bridge as a Starfleet member. Go to about the 1-hour-23-minute mark for a look.
Before she brought it in Bring It On and America's Got Talent, Union was unrecognizable in this 1997 episode as a Klingon, N'Garen, who makes fun of Worf's son.