http://www.slate.com/articles/arts/culturebox/2015/07/seinfeld_on_hulu_how_jerry_kramer_george_and_elaine_evolved_over_the_sitcom.html

Seinfeld was a self-described show about nothing in which nothing much ever changed. Between its first and ninth season, the show’s basic setup went unaltered. None of the four leads ever departed, and no new major characters were added. No relationships stuck. Jerry’s apartment and Monk’s Café remained the sitcom’s main settings.