The episode begins with a parody of Tales from the Crypt, with Mr. Burns as the Crypt Keeper. The scene begins in a dungeon room, where a crypt opens, and after several mice, snakes, spiders, and rabbits crawl out, so does the Cryptkeeper.

He proclaims himself to be the master of "scare-amonies" to the delight of zombie Smithers. A bound Moe interrupts in protest and is killed in an iron maiden, his blood spilling onto the floor and spelling out "Treehouse of Horror XVII". Moe himself takes delight in this and proclaims "Hey, my blood is a genius! Fancy Roman numerals and everything!"

As Homer and Marge make out in the backyard, a meteorite falls nearby, burning off the top of Marge's hair in the process. Cracking open, it reveals a green goo resembling a melted marshmallow. Despite his family's objections, Homer puts it on a stick and eats it. That night, his stomach rumbling from hunger, Homer eats all the food in the house. He also eats Snowball V and attempts to eat Bart but is stopped by Marge. Homer then becomes morbidly obese, and eats a teenager in an attempt to "saver" him from the flames of a barbecue fire.

Homer soon becomes a giant green blob, rampaging through the streets of Springfield, eating all the people he can find. As Homer samples bus passengers as if they were chocolates, Dr. Phil McGraw shows up with the Simpson family. He tells Homer to stop for their sakes. Homer ends his rampaging for fear of losing Marge and vows to use his insatiable appetite for more constructive purposes (he eats Dr. Phil anyway; his last words are "Food does not equal love!"). Later, Mayor Quimby dedicates a new homeless shelter. The homeless people enter the shelter, only to find themselves in Homer's gut.

At the end of an episode of Krusty's show, Bart goes backstage to complain about an acid-spraying Krusty brand alarm clock. Amid Krusty's various props, he notices the Golem of Prague, an ancient creature from Jewish mythology.

Krusty tells Bart that the Golem was sculpted from clay in the seventeenth century by a powerful rabbi, and will obey any order written on a scroll and placed in his mouth. Bart steals the Golem by writing a command for him to come to his house at midnight, while Krusty is distracted preparing for a pathetic "Desperate Houseflies" sketch.

At midnight, the Golem shows up at the Simpson's house. From then on, Bart uses him to carry out his commands: swinging Principal Skinner up and down like a yo-yo until he splits in half, killing the school bullies (Dolph, Jimbo and Kearney), and kicking Homer in the balls.

Lisa is outraged by her brother's antics, and believing that the Golem doesn't like doing the biddings of others, commands him to speak. The Golem — who talks and behaves like a stereotypical Jewish New Yorker — reveals that he does indeed guilty about being used to commit heinous acts.

After the Golem's constant neuroticisms start to get on the Simpsons' nerves, they create a Golem girlfriend for him out of Play-Doh. Voiced by Fran Drescher, she too proceeds to be a comical Jewish stereotype. The two clay beasts are married by Rabbi Hyman Krustofsky.

Chief Wiggum interrupts the wedding vowing to arrest the Golem for his rampage, but Mrs. Golem quickly distracts him with the promise of pan-fried chocolate bars.

The population of Springfield, October 30, 1938 (during the Great Depression), are fooled by Orson Welles' infamous The War of the Worlds radio broadcast and believe the world has been invaded. A mass panic breaks out, and the citizens begin rioting. Marge voices her belief that the Martians will only destroy humans, so Sideshow Mel suggests they foil the aliens by cavorting naked in the mud like animals. They do this until the following day, when Lisa notifies the citizens that it was all a hoax, and, angry at being fooled, the citizens of Springfield vow to never fall for such a trick again. Kang and Kodos decide this is the perfect time for a real invasion, and begin destroying what's left of the town.

True to their word, the town does not believe that it is a real invasion and ignores it. Orson Welles comes to Springfield, admits it is not a staged act, and begs them to do something. Unfortunately, they do not, and the segment ends three years later with Kang and Kodos looking over the ruins, mulling on what went wrong and why they weren't greeted as liberators, as they rid Earth of weapons of mass disintegration during Operation Enduring Occupation. The segment ends with the camera pulling away from the smoking ruins of what was once Springfield.