Susan tells George that she taped Mad About You (1992). However, in the episode The Apartment (1992) it is revealed that Paul has been subletting his old apartment to Kramer, thus putting "Mad About You" and "Seinfeld" within the same fictional universe.
When Jerry says, "I have a real problem with shushing!" his arms are spread and his coffee is on the table. In the next shot, he is holding his coffee near his face.
When Elaine, Kramer and Newman are taken to the police station, the exterior shots of the police car are of a 1994 Chevrolet Caprice, but the interior shots are of the older, square body style.
George (Jason Alexander) & Jerry (Jerry Seinfeld) go to see Firestorm at night, yet the outside of the theatre shows it's clearly day time.
At the end of the episode, when George and Susan are watching "Mad About You", for some reason, Susan appears to be laughing at the credits.
Ed O'Ross plays the one policeman of the two who actually has several lines of dialogue and appears in 2 scenes (at Kramer's door, and at Newman's door). Yet, inexplicably, O'Ross is omitted from the credits, while the other cop, who says nothing and essentially only stands next to O'Ross, is credited. If only one of the cops was to be credited, it should have been O'Ross since his role was far more significant to the plot.
When Elaine (Julia Louis-Dreyfus) enters Jerry's (Jerry Seinfeld) apartment to complain about the dog, a production mic can be seen above her for a few seconds.
At 8:59, George can be seen sitting on a bench marked "Santa Monica Pier" while supposed to be in New York.
The dog couldn't have gotten back inside the apartment building by itself.
When Elaine (Julia Louis-Dreyfus) calls Newman (Wayne Knight) about the dog, she picks up the phone and dials. She would never know his phone number by memory.
At about 3:23, at the very end of the scene where George and Jerry make their pact to "make some changes," the shadow of a boom mike sweeps over Jerry's hair.
George's chess game in the intro makes no sense. It is his turn, even though his opponent's king is in check; you can't end a turn with your king in check. They continue like this and she checkmates him... while in check herself.