- Divorced Installment: The movie was originally going to be an adaptation of the horror comic Rex Havoc before the story was completely rewritten.
- Franchise Killer: While a planned sequel got scrapped, DreamWorks still tried to turn the series into a multimedia franchise early on, with the movie getting animated shorts (Mutant Pumpkins from Outer Space, Night of the Living Carrots) and crossover video games (Madagascar Kartz, Dreamworks Super Star Kartz), but the failure of the short-lived TV series ultimately killed any further projects the studio may have planned, and the series itself hasn't seen any major acknowledgement beyond the occasional multi-franchise crossover like Dream Works Universe Of Legends.
- Missing Trailer Scene: The Team Shot of the five monsters marching purposefully toward the camera.
- Role Reprise: In a rarity for a movie full of Celebrity Voice Actors, Reese Witherspoon, Will Arnett, Seth Rogen and Rainn Wilson all reprise their respective roles as Ginormica, Missing Link, B.O.B. and Gallaxhar for the tie-in game.
- Playing Against Type: Paul Rudd is usually cast as the Nice Guy or a Jerk with a Heart of Gold, rather than the unrepentant, selfish Jerkass Derek.
- Stillborn Franchise: Much like its fellow DreamWorks movie, Shark Tale, Monsters vs. Aliens did well in its home country of America, but its poor overseas intake led to a sequel being scrapped. However, it did result in a short-lived TV series a few years later.
- Throw It In!: What you get when you hire an improv comedian. "Evidently they eat lead" was one of them.
- BOB's line "I think that Jello gave me a fake phone number." was ad-libbed by Seth Rogen.
- Viral Marketing:
- A rather believable (read: amusing) conspiracy nut website has teasers for the movie amid the alien coinage and mind-control candy.
- Nickelodeon created an ad which started out as a True Jackson, VP promo before abruptly going to static and then shifting to an announcement warning people of the arriving monsters.
- What Could Have Been:
- Several early promotional images for the movie depict Ginormica wearing a red version of her monster uniform, suggesting it was changed to black late into development. She also had brown eyes instead of blue.
- Susan's "Zombie Cheerleader" costume from the Halloween Special.
- A female Gallaxhar who is basically the parallel version of Susan.
- The original pitch was an adaptation of Rex Havoc and the Asskickers of the Fantastic, an obscure satirical comic from Warren Publishing (the same folks behind Vampirella). The monsters were mostly established by this point, although B.O.B. was called The Ick! and Ginormica was referred to as the 50,000 Pound Woman.
- The monsters would have been imprisoned in Alcatraz at the end of the second act. One draft had the monsters going on the rampage after Derek breaks up with Susan, while another had the President make them take the fall for the destruction of San Francisco.
- The Wiki Rule: Monsters vs. Aliens Wiki.
Trivia / Monsters vs. Aliens