Doppelganger

Doppelganger was the second villain introduced. He is a shape shifting something that can take the form of any human body... and apparently Grubby, too. His motives against Grubby aren't quite clear, so he's a bit confusing. He took Grubby's identity to frame him for crimes such as an airport bombing and assault with a wiffle ball bat, and in another episode took the form of a female Herbert for some Grubby Seduction. He has a secret hideout which is for some reason the garage behind Fort Grubby. His current whereabouts are unknown.