@2:52 - Somebody missed the cue to play the fart sound... that's why Hartman laughed.
Marge (Jan Hooks) dotes on the men in her family (Phil Hartman, John Lithgow, Dana Carvey, Jon Lovitz, Kevin Nealon) who loosen their belts, belch, pass gas and promptly fall asleep after the Thanksgiving feast. [Season 14, 1988]