Answer by taking a quote from the following article:

The Simpsons Movie is a 2007 American animated comedy film based on the Fox television series The Simpsons. The film was directed by David Silverman, and stars the regular television cast of Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria, Harry Shearer, Tress MacNeille, Pamela Hayden, Maggie Roswell and Russi Taylor, with Tom Hanks, Green Day and Albert Brooks in guest roles. The film follows Homer Simpson, whose irresponsibility gets the best of him when he pollutes the lake in Springfield after the town has cleaned it up following receipt of a warning from the Environmental Protection Agency. As the townspeople exile him and eventually his family abandons him, Homer works to redeem his folly by stopping Russ Cargill, the head of the EPA, when he intends to destroy Springfield.

For inspiration for the crowd scenes in the film, the production staff referenced a poster featuring more than 320 Simpsons characters. Groening said they tried to include every single character in the film, with 98 having speaking parts, and most members of the crowds being previously established characters instead of generic people. The series' regular voice actors: Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria, and Harry Shearer, as well as semi-regular performers Tress MacNeille, Pamela Hayden, Marcia Wallace, Maggie Roswell, Russi Taylor, and Karl Wiedergott, reprised their roles. Joe Mantegna returned as Fat Tony, while Albert Brooks, who supplied many guest voices in episodes, was hired as Russ Cargill, after he told the staff that he wanted to be part of the film. For "about a week", he was to reprise the role of Hank Scorpio, but when the character was omitted from the film, he ended up voicing Cargill.  The cast did the first of three table readings in May 2005, and began recording every week from June 2006 until the end of production. James L. Brooks directed them for the first time since the television show's early seasons. Castellaneta found the recording sessions "more intense" than recording the television series, and "more emotionally dramatic". Some scenes, such as Marge's video message to Homer, were recorded over one hundred times, leaving the voice cast exhausted.  The writers had written the opening concert scene without a specific band in mind. Green Day were cast in that role having requested to guest star in the show. Tom Hanks also appears as himself in the film and accepted the offer after just one phone call. Everybody Loves Raymond creator Philip Rosenthal provides the voice of the father in the "new Grand Canyon" commercial with Hanks. Due to time restraints, several guests who had recorded parts were cut from the film. Minnie Driver recorded the part of a patronizing grievance counselor in a scene that ended up being cut. Edward Norton recorded the part of the man who gets crushed as the dome is implemented, performing a Woody Allen impression. The staff felt the voice was too distracting, so Castellaneta re-recorded Norton's dialogue with a different voice. Isla Fisher and Erin Brockovich also recorded cameos, but their scenes were cut. Kelsey Grammer recorded lines for Sideshow Bob, who was to appear at several different points, but these scenes were also cut. Johnny Knoxville was also touted as a possible guest star.  Although he does not provide the voice, Arnold Schwarzenegger is President of the United States rather than then-President George W. Bush because, according to Groening, "in two years ... the film [would be] out of date". Brooks was nervous about the idea, noting that "[Schwarzenegger's] opinion polls were way down", and has said that they "were [hoping] he'd make a political comeback". The animators began by drawing an accurate caricature of Schwarzenegger, but one of the staff instead suggested an altered version of recurring character Rainer Wolfcastle as President. This idea was developed, with the design of Wolfcastle, himself also a caricature of Schwarzenegger, being given more wrinkles under his eyes and a different hairstyle.

were there other famous voices that are not on the regular show?
Tom Hanks also appears as himself in the film and accepted the offer after just one phone call. Everybody Loves Raymond creator Philip Rosenthal provides the voice of the father