What MJ episode?!

The one where Homer wears a pink shirt to work, gets send to a hospital, meets a fat bloke that claims to be Michael Jackson, voiced by Michael Jackson except for the singing parts, which were sung by a Michael Jackson impersonator and all of it credited to some made up name.

Has the “Lisa it’s your birthday”-song.

They must be thinking of John Jay Smith's guest episode.

CHALMERS: Yes, and you call him John Jay Smith despite the fact that the voice is obviously Michael Jackson's.