The episode in question had a scene with Jerry and George at the diner.
A Superman discussion was going on where Jerry was using the ketchup bottle to represent the red sun of Krypton, and the mustard bottle was the yellow sun of Earth.
I was in a bar when this was on, and they turned it away. I never saw that scene again, even in reruns, so I must be unlucky.
So anyone know what episode it was?