Bart suspects a rat in his circle of friends when all of his pranks backfire. Meanwhile, Homer grows attached to his rental car, which he gets to drive for a week while his old car gets repaired.

!! Tropes:

* BaitAndSwitchComment: When Bart reunited Nelson, Milhouse and Donny to talk about the rat, his comments suggested he figured out Donny was the one but he suspected Milhouse.
* ChekhovsGun: Bart's Blue Vines.
* TheMole: Donny was sent to infiltrate Bart's prankster circle.
* TooDumbToLive: Given that Donny was new to the organization, it should have been obvious that Donny was TheMole, but Bart somehow instantly assumed it was Milhouse.
* WeatherManipulation: Homer triggers a thunderstorm '''''inside the rental car''''' by having the vents on the driver's side put out heat, and the vents on the passenger's side put out air. At Bart's request, Homer turns on the rear window defogger, which triggers '''''a small tornado!'''''
* WholePlotReference: To ''Film/TheDeparted''.