on The Simpsons - but it remained a secret for 12 years. He voiced a character in a mental institution in the Stark Raving Dad episode, which aired in 1991, but, because of a contractual problem, Jackson had to be credited as John Jay Smith. His contribution to the classic cartoon series remained a rumour among fans until The Simpsons creator Matt Groening confirmed it really was Jackson when the episode was released on DVD in 2003.