The League of Villains is an alliance of villains that teamed up to destroy Jimmy Neutron. They had all be defeated by Jimmy in the past, some more than once. There are some villains that Jimmy had defeated that were not members.
Their meeting place was the Junkman's ship. They appeared in the episode of the same name but, by then end of the episode, Zix, Travoltron, and Tee had quit the alliance, and the rest were trapped in the past.
- King Goobot (leader)
- Finbarr Calamitous
- Beautiful Gorgeous
- The Junkman
- Zix, Travoltron, and Tee (formerly)
- Grandma Taters
- Baby Eddie
- Eustace Strych
- The villains were supposed to return in the planned season four. One of the overarching stories would've been about them escaping from prehistory, rebuilding their organization and planning the final blow to Jimmy and his friends. In the planned series finale, all of Team Neutron would've teamed up and defeated them once and for all.
- Meldar Prime, Dr. Sydney Moist, Evil Jimmy and Bueford Lee Stormshuckle are not in the League of Villains and are therefore the only four villains that don't appear in the special.
- The League of Villains are parodies of DC Comics' Legion of Doom, Secret Society of Super Villains, Brotherhood of Evil, Injustice League, Rogues and Marvel Comics' Masters of Evil, Brotherhood of Evil Mutants, Frightful Four and Sinister Six.