The Sniffing Accountant - S5-E4
Trivia: The blue jumper in the episode that Jerry wears, and that Kramer also ends up wearing that made people sniff appears in a later Seinfeld episode where George is dating the daughter of a welfare officer. She can be seen wearing it when they are sitting in George's car at one point.
Trivia: Not only was Michael Richards carrying an air conditioner the entire episode, he cut his lip on it as he was putting it into the trunk of the car.
Trivia: The man whose dog Jerry is stuck watching is named after Larry David's manager, Gavin Palone. (Palone is also one of the executive producers of Curb Your Enthusiasm.
Trivia: The Voice of the car thief who Jerry talks to on the phone is co-creator Larry David.
The Revenge - S2-E7
Trivia: The Voice of the unseen Newman was originally co-creator Larry David, but for American syndication, Wayne Knight's voice was dubbed in.
Trivia: The man who returns George's $20 bill and says "Sorry, your highness, but we don't accept bills with lipstick on the president", is the show's co-creator Larry David.
Trivia: When Jerry and Elaine discuss how evil Newman is, Elaine comments "Maybe he's an enigma, a mystery wrapped in a riddle." This quote from Winston Churchill was referenced in JFK (1991), which featured Newman actor Wayne Knight.
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: When Kramer is hosting the show and starts getting a little nervous about Jerry's "questionable material" he tells Newman to put on a tape and it starts playing some music while he talks to Jerry. The music that he puts on is the same music they used in the episode "The Pilot (2)" for the "Jerry" pilot.
Trivia: In the Seinfeld Finale, Jerry and George have a conversation in the jail cell about the positioning of a button on George's shirt. For those viewers who don't know or don't remember, that is why George asks, 'Haven't we had this conversation before?', because this is the same conversation that started off the series in the very first episode.
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: When Jerry is talking about going on a date with Miss Rhode Island, Kramer says "they're never in contention." He really wasn't exaggerating. At the time of the episode, the highest a Miss Rhode Island contestant placed was 3rd runner-up (1968) and other than that, they never were even in the top 15.
Trivia: Newman's appearance in the episode is an obvious reference to Harvey Keitel's character The Wolf in "Pulp Fiction". Before Newman arrives, Elaine mentions that he "makes problems go away" just like The Wolf. Newman even uses the same "If I'm curt" line.
Trivia: In the very beginning of the episode the person wearing the cape is none other than co-creator Larry David.
Trivia: Lauren Bowles, who guest starred in several episodes as a waitress at Monk's, is Julia Louis-Dreyfus' half-sister.
The Revenge - S2-E7
Trivia: The idea of George returning to work and pretending he didn't really quit was based on a real-life incident. Before co-creating "Seinfeld", Larry David once yelled at a "Saturday Night Live" producer and stormed off the set (he was a sketch writer), only to return the following Monday and act as if it never happened. He actually got away with it.
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.