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.
- Bait-and-Switch Comment: 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.Bart: Gentlemen, someone I thought I could trust...is a rat! Now let's see: [points to Milhouse] Is it my best friend? [points to Nelson] My other best friend? [points to Donny] Or a kid I just met? Donny...grab Milhouse's legs! He's the rat!
- Becoming the Mask: Donny was hired by Skinner to befriend Bart and his group, so he can inform him about Bart's pranks and thus foil them, but Donny eventually feels guilty for betraying Bart and saves him from Skinner and Chalmers by setting himself Bart's latest prank he intended to ruin.
- Chekhov's Gun: Bart's Blue Vines.
- Delayed Safety Feature: Well after Marge rear-ends Hans Moleman's car, the airbag deploys and smothers him.
- Inconvenient Darkroom Illumination: When Bart is chasing Donny, he turns on the light in a darkroom and thus ruins all of Martin's pictures, including photos of a Flying Saucer, Nessie and Martin posing with Elvis.
- The Joy of X: Lisa is seen reading a book titled The Joy of Sax.
- "Kick Me" Prank: Bart spray-paints "Kick Me" on Skinner's suit. Skinner fixes this by changing it to say "Kick Mediocre Study Habits". Kearney sees this, sits down, and starts reading a book.
- The Mole: Donny was sent to infiltrate Bart's prankster circle.
- Noodle Incident: Nelson mentions several previous times they've egged things close to Skinner.Bart: We're gonna egg Skinner's house!Nelson: We've already egged his car, his office and his father's grave.
- Rule of Symbolism: The episode takes a memorable shot at the use of this in The Departed.Ralph Wiggum (pointing out the crawling rat in the final scene): The rat symbolizes obviousness!
- They Really Do Love Each Other: Invoked in this exchange after the Mentos explosions:Chalmers: SKINNER! [concerned] Skinner?Skinner: I'm alright, sir!Chalmers: Don't ever scare me like that again!
- Weather Manipulation: 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!
- Whole Plot Reference: To The Departed, with a bit of the Recess episode "The Spy Who Came In From the Playground" thrown in as well.