"Homer vs. the Eighteenth Amendment" is the eighteenth episode of Season 8.
When Prohibition hits the town of Springfield, Homer goes into the booze making business with Bart's help.
It is Saint Patrick's Day, and Bart obliviously arrives at school in his usual attire, resulting in him being pinched en-masse by the entire student body. The town of Springfield celebrates the holiday by drinking a large amount of beer. At the parade, Bart buys a plastic novelty horn. When a Duff Beer float sprays free beer, most of it goes into Bart's horn, making him drunk. A group of women complain to the mayor that they should ban all brands of alcohol. The keeper of the town laws goes over some old texts and discovers that a Prohibition law has been around for 200 years, but has never been enforced. Quimby has no choice but to ban alcohol from Springfield. This news causes all of Springfield's alcoholics to faint (such as Homer and Barney).
All the beer barrels are buried in the dump and Duff goes out of business shortly after releasing Duff Zero (thinking that their customers drink Duff because it tastes good and not simply to get drunk). The mafia begins providing beer illegally, bribing the police force to turn the other way. Even though a Prohibition law has been passed, everyone goes to a nearby speakeasy, disguised as "Moe's Pet Shop", for beer and dancing. The ladies against beer enter the bar and see Chief Wiggum drunk and dancing. They demand they bring in a police chief who will enforce the law. They send a telegram to Rex Banner to get to Springfield. Banner arrives and takes over as police chief, leaving Wiggum jobless.
Homer, who dislikes the no beer methods of Banner, figures out a way to keep Moe's bar operating through bootlegging. One night, he and Bart sneak out to the city dump to reclaim the beer that was disposed of when the Prohibition law was about to be enforced. He then sets up shop in his basement pouring the beer into hollow bowling balls. With the use of an intricate set of pipes under the Bowl-a-rama, he bowls the balls into Moe's, and in return, Moe puts the money in the bowling balls and sends them back.
Marge and Lisa later catch him, but Marge compliments him for doing so since it is the most brilliant thing that he has ever done over his years of stupidity. She also adds that the law is unjust and is amazed of how much money Homer has made. Lisa, on the other hand, objects over this idea, but is unanimously sent to her room by the entire family.
The media realizes someone is allowing Springfield's underground alcohol trade to flourish, and they give the still-unknown Homer the nickname "Beer Baron". Rex investigates, but finds no evidence. He vows to catch the Beer Baron and soon resorts to stopping people in the street to question them, including Ned Flanders.
Homer runs out of beer from the barrels, so he plans to start making bootleg hard liquor when Moe gets irritated at him for the beer shortage. This proves difficult as he not only has to place a suspicious order for 42 bath tubs but his stills keeps exploding. He observes Wiggum in an alley at night and plans to help him in this tricky situation. He gives his story to Wiggum so he can get his job back; however, Homer is punished for his illegal alcohol supply and he is going to be sent away by catapult.
Marge tells the town how silly the law is, but Rex interrupts saying that they don't get to choose which laws they follow and which they don't. They see him step on the catapult and Wiggum sends him "back to Mama". An old clerk reads the laws and discovers the law was repealed 199 years earlier. The mafia fills the town with beer within four minutes and everyone is drunk and happy again. Homer then finishes the episode by giving a toast to alcohol - "the cause of, and solution to, all of life's problems".