Stunt casting is a long tradition in science fiction and fantasy, but it's only gotten more common lately. Films and TV shows will cast a famous actor — or someone who used to be in a Joss Whedon show — to spark interest. Sometimes, it's just unnecessary. But here are a bunch of cases where it was the perfect casting.

Alec Guinness in Star Wars

Despite his legendarily strained relationship with the Star Wars films, Guinness complemented the cast of unknowns in the original trilogy, adding gravitas and legitimacy both with the quality of his performance and with his history in David Lean films — which had inspired so much of the Star Wars aesthetic.

Laurence Olivier, Claire Bloom and Maggie Smith in Clash of the Titans (1981)

Back in 1981, it seemed kind of strange that Clash of the Titans boasted such over-powered guest stars. But they definitely were among the most memorable things about Titans, along with Ray Harryhausen's creature effects. And they brought some much-needed gravitas to one of our childhood favorites. See also: Max Von Sydow, Brian Blessed and Chaim Topol in Flash Gordon.

Deborah Harry in Videodrome

Genre films from the 1980s are jam-packed with examples of somewhat questionable rock star stunt casting (see Tina Turner in Mad Max: Beyond Thunderdome, Sting in Dune, and Mick Jagger in Freejack.) But Debbie Harry was always weird, and Videodrome is so weird, that this role makes perfect sense.

Grace Jones in Conan the Destroyer

With Arnold Schwarzenegger reprising his first major post-Mr. Universe role, and in a movie also featuring Wilt Chamberlain in his only acting attempt, it's hard to say what the "stunt" is here. Still, as one of several actresses in the cast of this beefcakey movie, Jones is wonderfully weird — and more than a little scary.

David Bowie in Labyrinth

Another piece of 1980s rock-star casting that worked perfectly — mostly because David Bowie was basically his character, Jareth the Goblin King, throughout the 1980s.

Andre the Giant in The Princess Bride

André René Roussimoff had had a few small parts in mostly B-movies toward the end of his wrestling career, most notably as a sasquatch in The Six Million Dollar Man, and as Dagoth in Conan the Destroyer. Yet he's brilliant as a giant in The Princess Bride, displaying absolutely precise comedic timing and a flair for the fairy-tale romance. He became one of the best things about this storied movie.

Tom Cruise in Interview with the Vampire

Less a "stunt" than cold hard capitalism, Cruise's casting, which the studio insisted upon, seemed inexplicable even to casual fans, and Anne Rice famously disparaged it. Yet Cruise turned in a convincing performance, which began his transition from pretty-boy to somewhat more serious actor.

George Carlin in Bill and Ted's Excellent Adventure

He was never that much of a movie actor, but Carlin's persona, both intellectual and profane, helped made this genre comedy (that could have easily become something like Encino Man) into something more substantial. Carlin's character, the Gandalf to Bill & Ted's Fellowship, stands as one of the enduring pieces of his legacy.

Sean Connery in Robin Hood: Prince of Thieves

This is an awful movie — but the casting of Sean Connery as an uncredited King Richard is perfect for a couple of reasons. It's a nod to Connery's 1976 performance in Robin and Marian, and it's a coup de grâce for Connery's career as an actor who frequently makes brief appearances in random genre films. (See also: Sean Connery's wonderful appearance in Time Bandits.)

Whoopi Goldberg in Star Trek: The Next Generation

Goldberg was at once too big a star in the 1990s, and too much of a comedian, to belong easily within the Next Generation universe. Yet she brought to Guinan a reverence for the Star Trek franchise and a sense of seriousness, despite the ridiculous costumes, that made her a pretty reliable recurring character. And as Picard's besty, she gave Patrick Stewart someone with equal presence to play to.

Judi Dench in the James Bond films.

Dench joined the franchise during the irreverent Pierce Brosnan era, which converted Bond to an almost comic hero. Indeed it was her line, calling Bond a dinosaur, that transitioned him from a hero to a winking, self-aware, Austin Powers-era, swinging-sixties leftover. But Dench also helped reinvent the franchise twice. As the only actor that carried over from the Brosnan era to the much more serious, and more artistically ambitious, Daniel Craig era, Dench became the thread that held Bond's continuity together, as well as the voice that reminded us that this wasn't our grandparents' James Bond.

Samuel L. Jackson in the Star Wars prequels.

What's particularly fun about SLJ in these films is that he plays Mace Windu as if he's being directed by frequent collaborator Quentin Tarantino. He's the only one who seems like he's enjoying himself. His purple lightsaber would seem to confirm that he — and presumably no one else in this cast — was allowed to have a good time with the character.

Anthony Hopkins as Odin in the Thor films.

He's sort of emblematic of Marvel's casting strategy in a lot of their recent films: go for an edgy A-list supporting actor, who can bring an unexpected gravitas to the character. There were rumors that Brian Blessed was going to play Odin in Thor, but Hopkins probably wound up bringing more seriousness and intensity. See also, Jackson as Nick Fury.

Winona Ryder in Alien: Resurrection

Casting Ryder as this film's requisite android gestured at Ryder's own reputation for an emotionless and bored-seeming acting style. Although this film seemed to offer Ryder a much-needed opportunity for reinvention, in the end she was the one who helped give the Alien films something new and interesting.

Ian McKellen in X-Men

In the vein of Judi Dench as M, Ian McKellen was another British actor with serious theater and art-film chops whose casting in a genre film came as something of a surprise, first as Magneto and then, arguably less of a stretch, as Gandalf. Yet he's perfect, and his X-Men career has also enabled us to witness his wonderfully goofy and tender friendship with Patrick Stewart.

Katee Sackhoff in Battlestar Galactica

Casting a woman in the stereotypical role of the cocky fighter pilot is almost the definition of "stunt." Yet Sackhoff's performance, and the show's quality, kept the rebooted Starbuck out of stereotype territory. It's a role and a performance that has — unfortunately — not been duplicated since.

Heath Ledger in Dark Knight

Even before Dark Knight, there was already a sense that Ledger was an actor whose history as a heartthrob had underutilized his acting abilities. Brokeback Mountain started his transition, but his Joker was an absolute revelation, and his death before the film's release only added to the mythologizing of both his abilities and his penultimate role.

Michael Caine in the Batman films

Caine's casting as Alfred came as a bit of a surprise. He commands so much respect as an actor that it was hard to see him in the supporting (literally!) role of a butler. Yet like Dench and McKellen, he brings skill and tradition to a franchise film. Casting of this caliber is one definite reason for the current superhero renaissance.

Bill Murray in Zombieland

Clearly a stunt. Bill Murray plays himself living alone in his decaying mansion, fooling attacking zombies by employing special effects makeup. And Murray absolutely suits the tone of this irreverent movie, in which we're all in on the joke.

Kevin Spacey in Moon

As GERTY, Spacey brought some star power to this relatively small film. As just the voice of GERTY, Spacey was able to make his contribution in a single afternoon. Thanks to Spacey, the character of GERTY, a computer programmed to assist his human user, has a lot more depth and nuance than it might in the hands, or voice, of a lesser actor.

Mary Elizabeth Mastrantonio in Grimm

It was pretty surprising to see this intellectual and serious actress show up as Nick Burckhardt's badass mom. In the style of Sackhoff's Starbuck, Mastrantonio eschews overt sexiness and other cliches, playing Kelly Burckhardt as all understated, quiet toughness.

Amy Acker in Person of Interest

Acker is just one of the Joss Whedon alums who have become genre stalwarts, showing up any time a science fiction or fantasy TV show wants an attention-getting guest star. (See James Marsters and Anthony Stewart Head, plus almost the entire cast of Firefly.) So when Person of Interest cast her as Root, the geekiest character on the show, it might have been just a fun shout-out to the show's geekier viewers. But instead, Amy Acker's complex and incandescent performance has become one of the show's biggest assets. It's hard to remember she ever played any other roles.

Robert Redford in Captain America: The Winter Soldier

What makes Redford's casting different from Dench's or Samuel L. Jackson's is that TWS uses Redford's status as part of an elaborate deception. You automatically trust Robert Redford, so when — like almost everybody else in this film — he turns out to be somewhat deceptive, it's a great surprise.

Bill Paxton in Agents of SHIELD

Fresh off of Big Love, Paxton might have seemed out of reach for a network drama. Yet Agents of SHIELD played on both his regular-guy qualities, and his history in science fiction, to make him an endlessly entertaining guest star. Honestly, I was pretty sorry to see him go.

So... who did we leave out?