Basil Karlo was once a famous actor, but soon fell into madness after he learned that one of his classic movies was being remade with a new star in his previous role. Fashioning himself in the mask of the movie's villain, Clayface, Karlo assumed the character's name as his new identity and murdered several of the cast and crew before being apprehended by Batman and Robin. Using a substance from a group known as The Mud Pack, Karlo gained the appearance of a massive monster of clay, able to shape-shift into anybody he wishes to.