18 Trilogy of Error

Each short begins at sunrise, when the garbage men are doing their morning route. They pick up all other trash cans but accidentally pick up Ned's mailbox, causing him to say: "Son of a diddily!"

At 7:03 A.M, while Homer is applying deodorant, Marge shouts out that breakfast is ready. Homer runs downstairs, but is surprised that Marge is serving a gooey cereal called "Mueslix." Lisa gets Homer out of the mess by showing him her school science project, a robot named Linguo, who corrects grammar. Homer breaks it by pouring beer down its throat, and Lisa runs upstairs frustrated. Meanwhile, Homer tries to get a brownie from Marge, who will not let him. Whilst cutting them, Marge accidentally severs Homer's thumb. As Homer retrieves his thumb from Santa's Little Helper who escapes to the Flanders' house, Marge calls 911. Chief Wiggum picks up, and mistakes the incident for attempted murder. He asks for the address so he can arrest Marge, making her lie, claiming it is 123 Fake Street, which Chief Wiggum believes. They drive off to the hospital, but on the way, they crush Rainier Wolfcastle's Ferrari. While he is trying to break the Simpsons' car, they sneak into the Ferrari.

Once at the hospital, Dr. Hibbert claims that the insurance will not cover the cost, so they drive towards Dr. Nick's clinic. Since Homer's thumb is starting to shrivel up, he stops by Moe's, where he gets a pickle brine solution. He gets distracted by drinking a beer, and because of his major blood loss, he passes out, saying random words. Barney Gumble wakes him up with coffee, and just as Homer rushes out the door, he sees that the Ferrari is gone. So, he hitchhikes (which at first does not work, because he has no right thumb), but Cletus' pickup truck eventually stops by. He drives Homer to Dr. Nick's, but when they leave the truck, they discover that the clinic is on fire. Just as Homer asks Cletus to drive him to Shelbyville Hospital, the truck gets stolen and Homer trudges along the roadside, and sees that he still has twenty miles to go. Since his thumb is fading again, he is just about to throw it away, but gets distracted when he sees Linguo's severed head next to him after shooting from town.

Thanks to Homer, Lisa has to fix Linguo, and misses the school bus as a result. Finding her bike gone and seeing her parents leaving for the hospital, she runs to school but on the way gets a ride from Krusty. However, Krusty and Mr. Teeny mistakenly take her to the West Springfield Elementary School. While there, Lisa meets a boy named Thelonious, who is similar to her. After spending time with him, Lisa leaves the school and, needing a ride, stops at Moe's Tavern looking for her dad. Homer is not there, but she finds Chief Wiggum listening to a conversation between a wired up snitch and some gangsters over the radio. She identifies a voice as Fat Tony's. This causes Wiggum to speak into the receiver "Fat Tony, is that you?" and on the radio Louie, one of Fat Tony's henchmen says "This guy is wearing a wire" following what sounds like gunshots. As she leaves the tavern Homer comes in. Outside, Lisa finds Marge, who takes her to school, however the car runs out of gas as Marge does not understand how to read the Italian gas meter. Marge and Lisa see Cletus' truck and hitch a ride, but when he exits his truck they steal it and drive to the school themselves. They never arrive because Bart emerges from the manhole in front of them.

The doorbell rings, and Bart answers it. It is Milhouse, who has found something in the woods. To get there, they ride Bart and Lisa's bicycles to the woods and find a cave full of fireworks. Bart tests some, only to blow up Dr. Nick's clinic. Bart and Milhouse hide in a building which is addressed 123 Fake Street, the address that Marge gave to the police. They are caught by the police and asked to help find the person selling the fireworks. Bart and Milhouse find Fat Tony but a voice comes out of the speaker hidden in Bart's clothes, saying "Fat Tony, is that you?". Fat Tony realizes that Bart has a wire and Bart lights the fireworks in Tony's hand to escape. Fat Tony chases the boys through the sewers until they emerge where Marge and Lisa are. Having been chased down the street, Bart and Milhouse get cornered. To save the boys, Marge throws Linguo at the gangsters and due to the mobster's bad grammar, the sparks from Linguo's body caused by the overload ignited the fireworks causing Linguo to explode, which also takes down the mobsters.

Fat Tony gets arrested, and Homer expresses gratitude that no one was hurt, but Marge points out his severed thumb and Lisa's destroyed science project. Fat Tony offers a solution to their problems. Lisa brings the mobsters to the science fair, and Legs (one of Fat Tony's henchmen) successfully reattaches Homer's thumb while Lisa narrates the presentation for her class. Lisa gets an A for her presentation. The episode ends with Mr. Teeny jumping into Marge's arms and saying (with subtitles) that the episode's plot made no sense.