In 1989, Richards was cast as Cosmo Kramer in the NBC television series "Seinfeld", which was created by fellow "Fridays" cast member Larry David and comedian Jerry Seinfeld. Although it got off to a slow start, by the mid-1990s the show had become one of the most popular sitcoms in television history. The series ended its nine-year run in 1998 at No. 1 in the Nielsen ratings. In the setting of "Seinfeld", Kramer is usually referred to by his last name only and is the neighbor of the show's eponymous character. Kramer's first name, Cosmo, was revealed in the sixth-season episode "The Switch".