 Cartman s mother is going out to a meteor-watching party, and leaves Eric with Shelley Marsh (Stan s sister) as his babysitter. Once Mrs. Cartman leaves, Shelley invites her boyfriend, Skyler, who in turn invites his entire band to practice in the living room. Desperate to get them out of the house, Cartman tries one scheme after another, but nothing works. Only when Shelley gets cruelly dumped does Cartman begin to see her side of things, and the two team up to get revenge.