Elain's New Yorker cartoon in a 1998 episode of Seinfeld actually made it into the real-life New Yorker

George's costume designers intentionally made his clothing one size too small to make his appear unhip

Julie Louis-Dreyfus did not appear in the pilot episode of Seinfeld

In the first episode of Seinfeld, Kramer's last name was Kessler. Producers were concerned that Larry David's friend Kenny Kramer (who was the bases for the character) would object to the use of his name. Eventually they worked out a deal and the character was renamed "Kramer"

Seinfeld was originally conceived as a one-off, 90 minute special called "Stand Up"

Jerry Seinfeld's former friend Michael Constanza sued the "Seinfeld" creators, claiming that the character of George was based on him and thus violated his privacy. He lost