Dr. Cornelius Colon (voiced by Peter Keleghan) - A mad proctologist, who plots to engulf the world in a gigantic colon, starting with Ringworm Junior High School (on the last day before its Summer vacation), to take revenge on people for unsympathetically making fun of him for his unfortunate surname. Has giant tapeworms as henchmen.
- First Appearance: Episode 18 ("School's Grossed Out for Summer")