Homer embraces the "old person lifestyle" when Grampa and two other octogenarians move into the Simpson home, while Nelson becomes friends with Bart, who defends Nelson's love for hand-me-down underwear.
Bart and his fellow underachievers are taken on a "field trip" to Capital City so that they can miss the standardized test, and Homer makes sure that nothing bad happens until their insurance goes back into effect.
Bart gets Milhouse to take the rap for a prank at school, and then blows him off when he falls for a cute 5th grade do-gooder, prompting Milhouse's wrath. Meanwhile, Lisa begins taking "happy pills" to improve her negative outlook.
Lisa becomes livid with Miss Hoover, and in a series of homages to classic Hitchcock sets out for deadly revenge. Next, Krusty's latest fast-food sandwich transforms news anchor Kent Brockman into an enraged zombie and twenty-eight days later, cannibal zombies have overrun Springfield. In the final frightening fable, Homer accidentally falls through a trapdoor in Moe's tavern and impales himself on the pipes of Moe's microbrewery. Moe serves the barflies a glass of delicious beer flavored with Homer's blood and Homer, now half-man, half-brewing apparatus, returns for ...
Bart meets the boy responsible for the greatest prank in Springfield Elementary School history, and discovers that he's now a 19-year-old loser. Meanwhile, Marge is scolded for providing unhealthy snacks for Maggie's play group.