Continuity mistake: In one scene George is solving a Rubik's cube in Jerry's apartment. When he leaves, he places the cube on Jerry's kitchen counter, and it is in the middle of the counter with the red color facing out. In the very next shot, it is moved much closer to the far edge of the counter and the color facing out has changed.
Factual error: In this episode, after accepting a free Armani suit from Kenny Bania, Bania insists that Jerry repay him by taking him to a nice restaurant. Jerry takes Bania to Mendy's, a Glatt kosher NYC deli. During the ordering process Bania suggests, "Oh, get the swordfish. Best swordfish in the city. The best, Jerry." Swordfish is considered an unkosher fish by Glatt kosher standards since it does not have scales, one of the essential criteria. It would therefore never be served at Mendy's.
Continuity mistake: While Kramer is explaining about being in the Woody Allen movie, George is in the background looking out the window trying to stop car alarms with his keys. Less then five seconds later, George ends up by Jerry's counter (without being seen) and has a can of Shasta in his hand. (00:08:40)
Factual error: In the episode where Jerry is upgraded to first class while Elaine struggles in coach, the scene changes to show a plane flying with the colors of Southwest Airlines, and you can make out the name "Southwest" written on the tail if you pause as it's landing. Anyone who has flown them knows that there is no first class on Southwest.
Continuity mistake: We find out George's parents sleep in separate beds. His father says "Thirty years ago we came to an agreement. It was the only way I could get some rest. Estelle's got The Jimmy arms." This contradicts S5E10, "The Cigar Store Indian", when George's parents come back from their trip, Estelle finds a condom wrapper in "our bed." Also Frank asks George, "You were having sex on our bed?", and Estelle follows by saying, "Who told you you could have sex in our bed?!" (00:16:50)
Factual error: When George tells Jerry about his date with Anna, he says he is picking her up in his father's 1968 GTO, but the car he is leaning on in the park is a 1967 GTO, which has a completely different body style.