The Crowded Snowglobe

Mad About You tried, by establishing that Kramer was subletting Paul’s old apartment. But in Mad About You continuity, Jerry lived in the building before Kramer moved in, while Seinfeld clearly showed on several occasions that Kramer was already living there when Jerry arrived. This means that Kramer exists in two different universes. Why do you think we never saw the inside of his apartment? Because it was a Warp Zone! We would have gone insane had we ever seen inside, as our mortal minds can’t comprehend the merging of separate realities.