The Simpsons Movie Audio Commentary Matt Groening

Homer's actions lead to a major environmental catastrophe after he irresponsibly dumps a silo full of pig manure into the recently cleaned Lake Springfield. The EPA, led by Russ Cargill, responds by encasing the entire town in a giant glass dome. An angry mob forms, and the Simpson family barely escapes through a sinkhole, eventually relocating to Alaska.  While the family starts a new life in Alaska, Homer sees a news report that the EPA plans to destroy Springfield. Marge and the children feel they must return to help their former friends, but Homer is initially hesitant. Ultimately, Homer embarks on a quest for redemption to save the town and his family, who are forced back under the dome by the townspeople. He successfully stops the bomb intended to destroy Springfield with Bart's help, and the dome is eventually broken.