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: George asks for a nickel from Jerry for his candy bar. He then proceeds to put only 3 coins into the machine for a $0.50 candy bar. No 2 coins would require a nickel to make 50 cents.
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)
The Frogger - S9-E18
Factual error: Frogger machines kept scores, but they didn't keep the initials of the person who got the score.
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.
Factual error: Elaine is placed in the same jail cell as the others. No police department anywhere in the U.S. would put a woman in the same cell as men.
Chosen answer: George does mention his brother in the episode "The Parking Space". They actually really never mention anything that contradicts the fact he had a brother though, it just isn't mentioned.