The League of Villains is an alliance of villains that teamed up to destroy Jimmy. King Goobot created this organization by joining several villains that had been defeated by Jimmy in the past, some more than once. Their meeting place was at The Junkman's ship.
In the cancellation of season four, there would've been an overarching story about the villains rebuilding their evil organization and planning the final blow to Jimmy. Had that come to be, Jimmy, his friends, and all the allies he made throughout the series would've battled them in the planned series finale. However, since DNA Productions went out of business, it's presumed that they were still trapped in prehistory. It makes this their official defeat (though Calamitous and Eustace would both make one more appearance later on).
- King Goobot V (leader)
- Professor Calamitous (formerly; escaped)
- Beautiful Gorgeous
- The Junkman
- Grandma Taters
- Baby Eddie
- Eustace Strych (formerly; escaped)
- Zix, Travoltron, and Tee (formerly; reformed)
- The League of Villains are parodies of the Galactic Empire from the Star Wars franchise, the Legion of Doom from Justice League and Super Friends, the Masters of Evil from The Avengers, the Deceptions and Predacons from the Transformers franchise, the Nazis from World War I and II, and the Soviet Union from the Cold War.
- Ooblar, Sydney Moist, Meldar Prime, Bueford Lee Stormshuckle, The Nanobots, Seymour, Gortox the Irritable, and Evil Jimmy are not in the League of Villains.