Frank (Jerry Stiller) states that he and Estelle (Estelle Harris) have slept in separate beds for thirty years, yet in an earlier episode George (Jason Alexander) claims to have had sex in their bed.
When Kramer wakes up to his door knob turning it is 5:30 on his alarm clock then after he puts the covers over his head it is 5:26 on his alarm clock.
When the exercise machine is hooked up to Kramer's (Michael Richards) door knob, the door knob turns both ways from the outside, yet from Kramer's view it only turns one way.
Jerry (Jerry Seinfeld) claims that Frank (Jerry Stiller) eats bacon and eggs for breakfast everyday, yet back in episode 8.6 The Fatigues (1996), he can be seen eating an omelette.
Jerry remarks that the Cadillac, a 1995 Fleetwood Brougham, had the Northstar System, which his parents hardly ever use. The Northstar System is another name for the Northstar V8, which was never available on any Cadillac Fleetwood.
You can't quit your job as president of a company and return and take back your old position.
When Elaine buys the coffee Elaine never pulls any money from her purse and pays for it.
Jerry (Jerry Seinfeld) lies to his parents about performing at Bally's and the Golden Nugget in Atlantic City. In 1986 the Golden Nugget was sold and renamed. Jerry should have known there was no Golden Nugget.
Jerry's (Jerry Seinfeld) parents explain why they want to sell the Cadillac Jerry bought them. Jerry asks "What about the Northstar system?" and Jerry's dad (Barney Martin) says "I don't think we've ever used it." Northstar is the designation of Cadillac's V8 engines of the time. Jerry was probably referring to Onstar which is strange for a self-proclaimed "car guy" who later hosted a show titled Comedians in Cars Getting Coffee (2012).