"Dark Knight Court" is the sixteenth episode of Season 24.
When Bart is falsely accused of playing a prank on the school band, Lisa defends him in student court; Mr. Burns is vengeance - he is the night (well, the early evening) - he is Fruit Bat Man.
Springfield is celebrating Easter and the school band is playing. However, Easter Eggs come out of the bells of the horns, landing on the crowd. After discovering Bart laughing, everyone chases after him. Mr. Burns and Smithers take a wander in the Android's Dungeon instead. Burns observes superhero comics and recalls his younger years of reading comic books but his father had burned down the comic book shop. At home, the family (save Lisa) accuse Bart of the prank when he swears he didn't do it. Lisa protests for a trial but finds it difficult to find a judge that likes Bart. Grampa tells Bart and Lisa the story of him meeting Janet Reno in 1998, which they refuse to believe.
At Burns Manor, Burns takes a liking to the Detective Comics, featuring Batman. He informs Smithers that he shall become a crime fighter, and he names himself Fruit Bat Man. The trial is held at Springfield Elementary and Superintendent Charmers reveals the judge to be Janet Reno, which show that Grampa's story was indeed true. The same night, Mr. Burns battles crime in Springfield but is unable to realize that Smithers is faking the crimes to protect Burns.
Lisa makes a plea for clemency but Janet denies the plea, making all of Bart's enemies (including Homer, Moe, Sideshow Bob and Apu) testify against him. At home, Lisa sees Burns as his superhero persona in the newspaper and makes a smug yet bold statement: "A Simpson never gives up" (to which the rest of the family laughs uproariously, including Maggie). Burns refuses to help Lisa after she asks for help and is outraged when he discovers that Smithers faked the crimes.
The next day, Lisa discovers a small splatter on Willie's kilt and they question him. Willie explains that he committed the prank because he hates Easter. Willie destroys the kilt to remove the evidence, but he got arrested and defeated by Burns, who chose to help Lisa after all. It was presumed that Willie was sent to Springfield Penitentiary for a few years for his actions and possibly lost his groundskeeper job. Bart is cleared of all the charges, and the same night, he tries prank calling Moe's Tavern. As the closing credits roll, a trailer for "The Dependables" is shown and the heroes start playing poker against each other.