The player directs small rats to an extermination area through complicated maze-like levels. The player controls Krusty the Clown, who must navigate through his Krusty Brand Fun House. Each level is a puzzle in which a number of rats must be exterminated. Using different objects and obstacles, Krusty must create a path for the rats to follow and guide them towards an extermination device. Other creatures such as snakes, martians, flying pigs and birds attempt to hinder Krusty's progress by injuring him; he must throw pies in order to defeat them.

In each stage the extermination devices are run by a different character, including Bart, Homer, Corporal Punishment and Sideshow Mel.

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