Vanity Plate: Gracie Films' appears at the end of the film in a homage to the television series; this is the first and only time to date the plate has appeared in a feature film produced the company. (A version of the logo would later appear on Maggie Simpson in: The Longest Daycare.)
What Could Have Been: Kelsey Grammer's Sideshow Bob and a family therapist voiced by Minnie Driver were originally going to be in the film, but for some reason their scenes were cut.
Hank Scorpio from "You Only Move Twice" was going to be the villain instead of Russ Cargill. Hell, they not only share the same voice actor, but the same voice. They decided against it because Scorpio was found to be too likeable to turn into an all-out villain.
The film was going to have more PG-13 language than just Marge's one "Goddamn."
Erin Brockovich was to make an appearance in the movie.
Apparently, it was originally supposed to be President Schwartzenegger who managed to KO Cargill (with a tree branch!), instead of Maggie dropping a boulder on him.
A Simpsons movie has been planned since the 1990s, but the writers couldn't figure out how to stretch the plot to feature-film length. Episodes that were considered for a feature-length movie are "Kamp Krusty" (which became the first episode of season four) and "Bonfire of the Manatees" (the first episode of season 17).
Instead of going to Seattle, Marge and the kids were going to go on The View where Russ Cargill shows up, gets in a shotgun duel with Joy Behar, and has the Simpsons arrested.
Isla Fisher and Edward Norton were going to make appearances but their scenes were cut.
And, furthermore, though many of these scenes were animated, and the producers claim the film changed so often that at least another film's worth of material made it to storyboard and/or animatic, only a few minutes of dull deleted scenes appear on the DVD.
Originally, Marge, not Grandpa was supposed to be the one to have the prophecy at church, but the writers admitted they were a little disturbed by the fact the the entire family would just ignore when someone like Marge would completely wig out, so they changed to the character that everyone ignored anyway.
Maile Flanagan was the original voice actress for Colin, but she was let go at some point in production and Tress MacNeille re-recorded the character's dialogue.