Continuity mistake: In the episode with Bette Midler, she is injured when George tackles her at home plate. When he hits her, she is knocked into somebody. When they show her again, she is sprawled against the backstop with no one behind or even near her that seems to be hurt. George also misses home plate.
Continuity mistake: When Elaine gets kicked out of the nail salon it is a clear day (in fact the whole episode is) then the next scene she meets J Peterman at night and in the rain. When she left the salon she is wearing a red blouse, no jacket. When she meets Peterman she is in a trench coat with a white blouse. The Peterman portion of this episode really makes no sense.
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.