Jason Alexander didn’t appear in one episode and he was not happy about it

In all but one of Seinfeld’s 172 episodes, George Costanza appears on screen at some point. However, he was nowhere to be found in the season three episode, “The Pen,” which has Jerry and Elaine visiting Jerry’s parents in Florida. Nervous and agitated that being written out of the episode meant that he could be written out of the show, Alexander warned Larry David that “if you do it again, do it permanently.” Needless to say, it never happened again.