The Cad and the Hat

Magnus Carlsen as himself
Seth Green as the Robot Chicken Nerd
Patton Oswalt as Bart Simpson's Guilt

"The Cad and the Hat" is the fifteenth episode of the twenty-eighth season of the animated television series The Simpsons, and the 611th episode of the series overall. It aired in the United States on Fox on February 19, 2017.

Lisa narrates the episode's events alongside Bart, describing her ups and downs of being Bart's sister, and proceeds to tell of a time when they had a bigger rift than usual, beginning when The Simpsons headed off for a fun vacation at the newly "safe" Springfield beachfront area (Mayor Quimby says that the dangerously polluted water isn't better in any way, it's just been classified that way after the safety standards were lowered). Bart is left saddened by the failure of his "Bad to the Bone" temporary tattoo, while Lisa finds a new sunhat that makes her ecstatically happy. However, Bart isn't one of them; angry over both Lisa's good fortune and that not waterproof tattoo, he takes her hat while she's sleeping in the car and tosses it out the window into a junkyard. When Lisa finds out her hat is gone, she is inconsolable, and Bart gets the first of an increasingly grotesque and uncomfortable visits from his "guilt monster", a slime-covered creature who sounds like Patton Oswalt and reminds him of what he did. Every time Bart denies his guilt, the monster grows and gets progressively hideous. Bart finally cannot stand the guilt and tells Lisa the truth, and she promptly declares it's a "wound that won't heal" and refuses his desperate attempts to make amends with her. After a while, Bart goes back to the junkyard and finds out the hat, named "Sunny", is now part of a car that was crushed into a cube. He uses the combination of Rod and Todd Flanders' Jesus-like powers and the acidity of Buzz Cola to break through the car and retrieve Sunny. However, when he presents Sunny to Lisa, she first says that she meant their relationship is over and that he should just focus on Maggie ("give her raisins, Bart, she likes raisins") and he sadly walks away. Lisa then has a vision from her own emotional spirit, angrily telling her "He's trying!" and she begins to cry and forgives Bart as they hug each other. Concluding her narration, Lisa notes that she and Bart are closer than ever and that they learned he indeed has a conscience. Nelson arrives and makes fun of Bart having a conscience and lets everyone know his mom is dating a gaffer on this TV show, much to Lisa's shock and the gaffer's embarrassment.