 According to at least one Internet source, Matt Groening (qv) has  confirmed that Michael Jackson (I) (qv) did provide the voice  (under the name John Jay Smith) for the character bearing his name  in the episode "Stark Raving Dad". He did not do any singing which  was done by an impersonator. Dustin Hoffman (qv)s appearance was  as Mr. Bergstrom from the episode "Lisas Substitute" where he was  credited as Sam Etic.