In Springfield, Lisa(Yeardley Smith) convinces the locals to clean up the polluted Lake Springfield after the sinking of the stage of the Green Day in a concert of rock and roll. Meanwhile, Homer(Dan Castellaneta) saves a pig from being killed in Krusty Burger and adopts it, calling the animal Spider Pig. After two days, Spider Pig fills up a silo with its excrement and Homer dumps the silo in the lake, polluting it. The angry population forces the Simpsons to move to Alaska. Meanwhile the stupid president Arnold Schwarzenegger is induced by his advisor from EPA to put a dome over Springfield to hold the population and destroy the city. When Marge(Julie Kavner) sees the news in the television, she tells Homer that they must return to Springfield to save their town and friends, but Homer is not convinced if people of Springfield deserve their support.