From Weezerpedia

Betsy was the name of the van used during the earliest days of Weezer. Originally called "The Enforcer", the van was found by Karl Koch and Patrick Wilson in Fontana, California. According to Alec Longstreth (who had access to reference photos from Karl for when he illustrated the jacket and label artwork for the 2019 fan club single, "It's Been So Long"), it was a 1985 Dodge Prospector van.

The band then purchased the van from a "dude who looked exactly like Mummar Gaddafi" (Koch). The van's name was at long last changed to Betsy when it became notorious for breaking down. It carried the band from town to town throughout America and even into Canada through 1994.

Betsy II

Betsy II is the fictional spaceship used in Songs from the Black Hole. Its name was inspired by the original van. The rooms are organized into "pods". Little is known about the ship.