500 Keys

Albert Brooks as Hank Scorpio

"500 Keys" is the twenty-first episode of the twenty-second season of The Simpsons. It first aired on the Fox network in the United States on May 15, 2011. It was written by John Frink and directed by Bob Anderson.

After returning from a shop that sells returned wedding cakes, Maggie gets locked in the car with the key inside. While searching for the spare keys (which soon proves unnecessary, as Maggie is able to free herself), the Simpsons discover a collection of keys to every door in Springfield. Lisa uses a key and finds a hidden classroom full of theater props underneath the school. She is intrigued by the discovery, and shares it with Principal Skinner, but when she brings along the school newspaper, they only find what is supposed to be behind the door, the "Banned Band Books". It becomes apparent that Skinner and Superintendent Chalmers are hiding something when they snatch the key from Lisa. She has the key replicated and returns to the door on her own, and finds the classroom is back; it had been hidden behind a phony set of bookshelves. She also sees a mysterious figure writing "The children are on Bus 23" on the chalkboard. Lisa is determined to solve the mystery of the hidden room.

Meanwhile, Bart tries causing mayhem with the keys but accidentally does good deeds with them, and ends up with the key to the city. Marge and Maggie find a key for a wind-up toy train called "The Pooter Toot Express", which makes farting noises when it moves. The toy gets away from them and they chase it throughout the city. Homer uses a key to get into the Duff Beer brewery with Barney and goes joyriding in the Duff Blimp.