Goop is a Polymorph (a word meaning "many shapes") from the Planet Viscosia (a play on "viscous"). He is a shape-shifting, self-regenerating, almost indestructible green blob that weighs 200 pounds. Goop can wrap his slimy body around his foes and throw them around. Goop's slime is controlled by a UFO-like machine over his head, which is actually an anti-gravity projector, and also where Ben's voice comes from. The UFO can cause the slime to take any shape and even hover off the ground. However, if the UFO and the slime are separated by even a short distance, the slime will become inert until the UFO recollects it. Goop's slime can be made acidic, as seen in "Good Copy, Bad Copy". Goop first appears in "The Gauntlet" when Ben battles an alien robot.