On New Year's Eve of the new millennium, Peter receives dire warning from a man in a chicken suit about the Y2K computer bug and the havoc it will wreak at the stroke of midnight. Terrified, Peter dresses the family in radiation suits and corrals them into the basement for the ringing in of the New Year. They are all disgruntled about missing their big plans, but when midnight finally arrives, so does Armageddon.
One week later, the world has barely begun to recover. Quagmire and Cleveland have fused together, Joe has melted into his driveway, and the entire town of Quahog is virtually uninhabitable. The Griffins set off in search of food, led by Peter's notion that the Twinkie factory in Natick is the most logical destination. When they arrive, they discover that the Twinkies survived the nuclear explosion. However, just as they enter the factory, Stewie comes into contact with nuclear waste that turn his arms into tentacles.
One year later, the town of New Quahog has been established with Peter as its permanent mayor. Of course,Peter makes all the wrong choices, insisting that everyone in town own a gun. Meanwhile, Stewie has become even more octopus-like and is multiplying, laying a large number of legs everywhere. Just before Stewie's offspring overrule the town, the Griffins are driven out of New Quahog. In the shows final minutes, Bobby Ewing reveals the entire episode was a dream and Quahog and the rest of the world were not destroyed by the Y2K bug after all.