The Jokester

The Jokester was Krusty the Clown's supervillain alter-ego after a nuclear explosion transformed half the people of Springfield into superheroes and supervillains.

History
When Bartman and Radioactive Man attempted to subdue the transformed Springfieldians by force, The Jokester placed a banana peel in Radioactive Man's path, then laughed as Radioactive Man slipped on it.

Behind the Laughter
He is based on The Joker.