The Simpsons attend an animation festival at the Springfield Convention Center. There, Homer takes an interest in a new process for motion-capture animation…and eagerly volunteers his services for a demonstration. Once Homer dons a special harness, a technician and company spokesperson explain that a cartoon dog on a nearby screen will now mimic his movements exactly. Homer then entertains the audience with various routines. He then enters a rest room to relieve himself…forgetting that he is still attached to the harness. Later, Homer informs Lenny and Carl that the device could be worth billions. He withdraws his life savings from the bank and purchases 500 shares of the company’s stock. Unfortunately, the firm declares bankruptcy and its owner flees to Brazil with the suit. Homer realizes his family is now broke.

Homer reluctantly informs Marge and the children that he wiped out their savings. Later, at Moe’s bar, Barney suggests that he raise some money by undergoing medical testing for research. As the testing gets underway, one of the researchers comments on Homer’s amazing stupidity. He and a colleague zoom in on an x-ray image of Homer’s brain and discover a crayon lodged within. In flashback, Homer recalls how, as a six-year-old, he stuffed 64 crayons up his nostrils, then sneezed violently, dislodging them (or so he believed). When the researchers tell him that a dangerous operation might vastly increase his thinking capacity, Homer undergoes the procedure. When he arrives home, Homer displays his mental prowess, much to Lisa’s delight. Lisa and her father spend time at the library, and later, Homer suddenly understands Frazier and proves there is no God. When Homer returns to work, he takes his job much more seriously and even sends a safety report to the National Regulatory Commission. Unfortunately, his report reveals criminal negligence, leading to the plant’s closure.

Homer becomes the most hated man in Springfield overnight, having cost everyone at the plant their jobs. After Homer is booted out of Moe’s bar, he tells Lisa that his brain has alienated him from all his friends. Lisa concurs, telling him that as intelligence rises, happiness decreases. She tells Homer that the best solution is to go for a long walk. While on his sojourn, Homer happens upon a movie theater screening a Julia Roberts film. Audience members notice that Homer isn’t enjoying the movie and advance upon him. Terrified, Homer flees. He makes his way to the lab, where he begs researchers to make him the “blissful boob” he once was. The researchers inform him that they do not play God…and hand him the name of an unlicensed surgeon: Moe Szyslak. Later, at the bar, Moe begins reinserting the crayon into Homer’s brain. While drawing a picture of her father, Lisa realizes that one of her crayons is missing. Anxious, she tells Marge that she fears the worst. At that moment, Homer bursts in the front door, lottery tickets in hand. Lisa realizes her father has returned to his old self. As Homer heads for the kitchen, an envelope drops from his pocket. Inside is a note that Homer authored before the crayon was reinserted in his brain. In the note, Homer tells Lisa how amazing she really is. Touched, Lisa hugs her father.