South Park Season 1, Episode 3: Volcano

Stan's Uncle Jimbo and his friend Ned take Stan, Kenny, Kyle, and Cartman on a hunting trip in the mountains, but Stan is unable to shoot a living target. Back in town, Randy Marsh discovers that the mountain is a volcano that is about to erupt, and the townsfolk dig a trench to try and divert the lava. Cartman tells the story of Scuzzlebutt, a mutant creature, and decides to dress up as the creature to scare the others.