The Contest - S4-E11
Trivia: While appearing alongside Jerry Seinfeld on The Tonight Show with Jay Leno, JFK Jr. revealed that people would constantly bring up his appearance in this episode, even though he never actually appeared in it and was only referenced.
The Airport - S4-E12
Trivia: When Elaine is talking to the male flight attendant about her meal that she ordered in advance, The Voice that answers out that he thinks he has her meal is co-creator of the show Larry David.
Trivia: The Green Peace worker in the boat at the end telling Russell that he will write to Elaine is series co-creator Larry David.
Trivia: In this episode, Susan finds letters from John Cheever (a real life writer) to her father exposing their relationship. Incidentally, in real life, John Cheever also had a daughter named Susan.
Trivia: While everybody blames George for nearly killing The Bubble Boy, it was actually Susan who pops the bubble. She's the one who hit the plastic divider that causes it to break and hiss as it leaked out the air.
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.