Factual error: During the entire series, the view of Jerry's door from the hallway is of a flat wall with the door in line, yet from inside The Apartment, not only does the kitchen angle into the hallway, but Jerry's fridge is recessed into the wall. The wall behind it should be blocking the hallway completely.
Factual error: Newman says that the "Magic Loogie" incident happened on June 14, 1987, when the New York Mets lost to the Philadelphia Phillies due to an error by Mets first baseman Keith Hernandez. However, the Mets played the Pittsburgh Pirates on that date, and the Mets won 7-3.
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.
Factual error: Kramer gives Jerry a two-line phone for his birthday, which Jerry plugs in and immediately uses. But a two-line phone requires the installation of an actual additional phone line. What Jerry was using when the NYU reporter overheard him "admitting" he was gay was simply call-waiting.
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.
Factual error: At the end of the episode in which George and Susan get engaged, they are lying in bed together watching "Mad About You" on TV. However, at some earlier point on "Mad About You" it had been established in a crossover episode that Paul Reiser was the person who lived in Jerry's apartment before him and was an old acquaintence of Kramer's, meaning that "Seinfeld" and "Mad About You" existed in the same reality. On "Seinfeld," the show "Mad About You" could not exist.
Factual error: During the AIDS walk there is an officer seen several times with a patch "Transit Police, NYC." Not only is the patch completely fictional, it doesn't look anything like the real transit police logo. The Transit Police had already been defunct by the time of this episode.
Factual error: When Jerry gets a speeding ticket, he asks Nicki to give the officer the registration. She gets a large piece of white paper from the glove compartment. That's what car registrations look like in California, where the show was produced. In New York, where it's supposed to take place, car registrations are the size of a driver's license, and are usually kept in the driver's wallet.
Factual error: In the scene where Anna is standing with George beside his father's GTO, Elaine suddenly runs in and pries her away from George. Elaine and Anna get into the cab. As the cab pulls away, the side door is marked as an NYC cab with a taxi license number, etc., but the license plate in the back is a California plate.
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.
Factual error: With the size of that red ball (approximately 2.5 foot diameter) and the density of oil (approximately 60 lb/ft^3), the giant ball of oil would weigh 491 pounds. This would be impossible for Kramer and Darren to lift out of the window and would definitely kill anyone it beaned.
Factual error: In the scene where Jerry, George, and Elaine are in the coffee shop and Kramer walks in with the dummy mailman with the bucket over his head, Kramer remarks how nobody entered the post office while he was outside protesting. Jerry remarks, "That is because it is Sunday." If that is true, how can the group be gathered at the coffee shop? There is a red sign by the entrance of the coffee shop showing the business hours, and the coffee shop is supposedly closed on Sunday.
Factual error: When Peterman is making a toast at his party, he quotes what he says is something said by the Papa New Guineans, and he proceeds to pronounce a sentence filled with clicks (lingual-ingressive consonants). However, this is impossible, as clicks are only used in southern African languages and three east African languages. (00:03:10)
Factual error: At several points during the case, the prosecutor introduces witnesses by saying "The state calls." Legally, Massachusetts is a Commonwealth, not a state, and that is how it is referred to in court. (See any episode of "Ally McBeal" or "The Practice.") However, even this would be incorrect here, as the episode makes it clear that the "Good Samaritan" law is a local Latham statute, not a Massachusetts law. In this case, "The people call." would be correct.