Revealing mistake: In the sequence when he gets shot by the FBI agents for stealing cable, Jerry Seinfeld is wearing ear buds, quite visible when he collapses by the door. Evidently the stage props even loaded with blanks were too loud for his taste. (00:09:00)
The Jacket - S2-E3
Continuity mistake: When Elaine's dad says "Pipe down, chorus boy" to George, suddenly a hotel staffer in red appears in the recess by the lamp. In another blatant continuity mistake, in the shot that follows George is suddenly without glasses. (00:17:50)
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.