Let's be honest for a second. DreamWorks Animation has always had this weird, almost chaotic energy when it comes to picking their actors. They don't just hire voice professionals; they hire massive A-list celebrities and hope the chemistry works. Sometimes it’s a miss. But with the 2009 flick Monsters vs. Aliens, they actually nailed it. It’s been well over a decade since Susan Murphy got hit by a meteor on her wedding day, yet the cast of Monsters vs. Aliens remains one of the most inspired lineups in CG history. You’ve got comedic heavyweights, sci-fi legends, and a pre-fame Rainn Wilson all mashed together in a tribute to 1950s B-movies. It shouldn't work. It does.
The Giant in the Room: Reese Witherspoon as Susan
At the heart of the story is Susan Murphy, later known as Ginormica. Reese Witherspoon was coming off her Oscar win for Walk the Line when she took this role. It’s easy to forget how much heavy lifting she does here. She has to play the "straight man" to a bunch of literal freaks while maintaining a sense of genuine heartbreak over her ruined wedding.
Susan isn't just a Kaiju; she's a woman dealing with a gaslighting fiancé, Derek Dietl, voiced by Paul Rudd. Rudd is great at playing the lovable guy, but here? He’s a total jerk. It’s a brilliant bit of casting because we naturally want to like Paul Rudd, which makes his character's narcissism even more annoying.
Why the lead worked
- Witherspoon brings a "girl next door" grit that makes her transformation feel earned.
- She avoids the "damsel in distress" trope by the second act.
- Her chemistry with the "monsters" feels organic, even though they were likely never in the same recording booth.
The Weirdos: Seth Rogen, Will Arnett, and Hugh Laurie
If Susan is the heart, the rest of the cast of Monsters vs. Aliens provides the pure, unadulterated comedy. Let's talk about B.O.B. (Benzoate Ostylezene Bicarbonate). Seth Rogen was essentially born to play a brainless, gelatinous mass. His distinct laugh and laid-back delivery make B.O.B. the breakout star.
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Then there’s The Missing Link. Will Arnett uses that gravelly, LEGO Batman-esque voice to play a prehistoric fish-man who thinks he’s still a macho heartthrob. It’s a hilarious contrast. He’s a monster who’s actually just a washed-up jock.
And we can't ignore Dr. Cockroach, Ph.D. This is where the casting gets high-brow. Hugh Laurie, right in the middle of his House fame, plays the mad scientist. He keeps the British accent, adds a manic giggle, and creates a character that is somehow sophisticated and disgusting at the same time. It’s a nod to The Fly, and Laurie sells the "mad genius" trope perfectly.
The Supporting Players and That President
Most people forget that Stephen Colbert is in this movie. He plays President Hathaway. It’s a perfect time capsule of 2009. Colbert was at the height of The Colbert Report, and his portrayal of a clueless, keyboard-playing President is legendary. The scene where he tries to communicate with the aliens using a synthesizer (playing "Axel F") is peak DreamWorks humor.
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Then you have Kiefer Sutherland as General W.R. Monger. This is a total 180 from Jack Bauer in 24. He’s playing a caricature of every tough-as-nails military man in cinema history. He’s loud. He’s aggressive. He has a strangely small body compared to his head.
The Villain Problem
Rainn Wilson plays Gallaxhar. Honestly? It's one of the few times a villain in these movies feels genuinely weird. Wilson uses a bizarre, modulated tone that feels lightyears away from Dwight Schrute. He’s an alien megalomaniac with a clone army, and while he’s not the most "menacing" villain in animation, he fits the 50s kitsch aesthetic like a glove.
Why This Specific Lineup Matters for Animation
The cast of Monsters vs. Aliens represents a specific era of Hollywood. It was that sweet spot where studios realized they could use star power to draw in parents while the slapstick kept the kids busy. But unlike some other films of the time (looking at you, Shark Tale), the actors here actually disappear into their roles.
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You don't just see Seth Rogen; you see a blue blob with no brain. You don't just see Hugh Laurie; you see a refined roach in a lab coat. This is the hallmark of good voice direction by Conrad Vernon and Rob Letterman. They didn't let the celebrities just "be themselves." They pushed them into the archetypes of horror cinema.
Fun Facts You Probably Missed
- Conrad Vernon, one of the directors, actually voiced "Insectosaurus." Well, he did the screams and grunts.
- John Krasinski has a tiny cameo as "Cuthbert." This was back when The Office cast was appearing in everything together.
- The film was the first ever to be produced directly in stereoscopic 3D, which is why some of the movements feel so exaggerated.
The Legacy of the Crew
Does the movie hold up? Visually, maybe it shows its age. But the performances are timeless. When you look at the cast of Monsters vs. Aliens, you’re looking at a group of people who understood the assignment. They weren't just there for a paycheck; they were there to parody the very genres that made Hollywood famous.
If you’re revisiting this movie today, pay attention to the dialogue timing between B.O.B. and the President. It’s some of the best comedic pacing in 2000s animation. The film didn't get a theatrical sequel, which is a bit of a shame given the chemistry of this group, though it did spawn a TV series and several specials. However, the original voice cast didn't return for the Nickelodeon show, and you can really tell the difference. The soul of these characters is tied directly to the voices of Witherspoon, Rogen, and the rest of the gang.
Actionable Insights for Fans and Collectors
If you want to dive deeper into the world of these characters or find more content featuring this specific ensemble, here is what you should do:
- Track down "B.O.B.'s Big Break": This is a 3D short film included on the Blu-ray/DVD releases. It features the original cast and serves as a prequel to the movie, showing how the monsters tried to escape Area 52.
- Watch "Mutant Pumpkins from Outer Space": This Halloween special also features the original movie cast. It’s one of the rare times the A-list stars returned for a television spin-off, and it captures the same vibe as the film.
- Check out the "Art of Monsters vs. Aliens" book: If you’re a fan of the character designs—specifically how they translated the actors' expressions into monster faces—this book is a goldmine of production history.
- Compare the Voice Acting: For a masterclass in voice range, watch an episode of House and then watch Dr. Cockroach. It’s a great way to appreciate what Hugh Laurie brought to the table beyond his most famous live-action role.
The film is currently available on various streaming platforms, and while it might not be the most famous DreamWorks property, the talent behind the microphones ensures it stays a cult favorite for those who love a good sci-fi spoof.