A prankster puts rotten eggs in the elementary school band brass section, causing an egg-filled mess when the students blow the eggs free. Bart is blamed for the prank when he is caught laughing at the chaos. After convincing his family that he is innocent, Lisa defends him in Youth Court with former Attorney General Janet Reno sitting as the judge. Lisa's case is going well until she opens the door on character witnesses. Meanwhile, Mr. Burns renews his interest in comics and decides to masquerade as superhero known as "Fruit Batman." Smithers helps his employer out by paying people to act as though he saved the day. But Mr. Burns is actually able to help Lisa when she finds out that Groundskeeper Willie was actually behind the prank. Burns captures the escaping Willie and forces him to confess in court.