- Dan Castellaneta (Homer Simpson / Abe Simpson / Barney Gumble / Krusty (voice))
- Julie Kavner (Marge Simpson / Patty Bouvier / Selma Bouvier (voice))
- Nancy Cartwright (Bart Simpson / Nelson Muntz / Ralph Wiggum (voice))
- Yeardley Smith (Lisa Simpson (voice))
- Hank Azaria (Moe Szyslak / Chief Wiggum / Apu / Comic Book Guy / Carl (voice))
- Harry Shearer (Ned Flanders / Mr. Burns / Smithers / Skinner / Lenny (voice))
The Simpsons — S22E21
Episode: 500 Keys
Air Date: 2011-05-15
Runtime: 23 min
Overview
After finding the keys to every door in Springfield, Lisa finds a hidden room beneath the elementary school.