Big, fat, dead...it has to be SAM KINISON.
He died in a carr acident later, I think 1991 or something, however, after the AAA was recorded.

And the song is WILD THING - a TROGGS cover. Richie also plays guitar on the version from Sam Kinison's album and he also appears in the videoclip along with Aerosmith, Slash, Billy Idol and many more.

i don't remember any other fat musician in a theater...