The Simpsons find a bunch of keys and try to find a use for all of them, one of which leads to the mystery behind a secret, technologically-advanced classroom at Springfield Elementary.

!! Tropes:

* BreadEggsBreadedEggs: Lisa found a three-door set. Their labels read: "Band Books", "Banned Books" and "Banned Band Books".
* BrokenRecord: Nelson when he's teasing Lisa for always following the rules. "Have a nice day, just like yesterday...and the day before that...and the day before that...and the day before that..." He even continues over the intercom while giving the morning announcements.
* CantGetInTroubleForNuthin: Bart tries to use some keys to pull epic pranks, but each time he ends up helping people.
* CassandraTruth: Rodd and Todd not believing their father when he told them the farting noise wasn't his.
* DidISayThatOutLoud: When Otto learned [[spoiler:those dead kids were actually dummies, he commented that he killed that hobo for nothing]].
* [[spoiler:FakingTheDead: To cover up the fake classroom, Skinner and Chalmers arranged a bus accident to explain what happened to the advanced students. The bus was actually full of dummies, but Otto was not informed of that and had been wracked by guilt ever since.]]
* ShoutOut: The fake classroom's chemistry side had the elements (fire, water, earth and air) represented by the symbols used in ''AvatarTheLastAirbender''.
** Also, when Lisa asked Nelson about Bus 23, he called her Literature/{{Goldilocks}} and told her those were bowls of gruel she'd rather stay away from.