Mad About You (1992) - 4 mistakes in entire show

Deliberate "mistake": The first 10 episodes of Season 5 were shot in a totally different order than they were aired. As a result, Jamie's size during her pregnancy is very inconsistent at the beginning of the season. In particular, she gets much smaller between episode 8 and episode 9 because episode 9 was originally supposed to air earlier in the season.

Continuity: Jamie and Paul are at the supermarket, and Jamie is eating chips. She leans on a coin operated horse. The bag of chips in her right hand changes from front (Green Label, "Baked Lays") to back view in one shot then to front view again.

Plot hole: In this episode, a very star-struck Paul meets Jerry Seinfeld on the street. It's not clear whether Jerry is playing himself or his Seinfeld character, but either way it's a mistake. If Jerry was playing himself, it's a mistake because Mad About You did a crossover episode with Seinfeld in its first season, so it would be impossible for Seinfeld (the TV show) or Jerry Seinfeld the actor to exist in the Mad About You universe. If Jerry was playing his character, it's a mistake because it was established in that crossover that Paul and Jerry used to be neighbors and knew each other fairly well, so Paul wouldn't be at all star-struck.

Continuity: In 2006, after Paul learns that Jamie is pregnant with their second child, Paul buys her a double baby carriage as a present. He says "Two kids, one carriage. One big happy family." A sweet gesture, but in the year 2006 Mabel would be 8 or 9 years old, far too old to ride in a stroller.