What is the nickname of this famous character featured in a season 7 episode of Seinfeld?

This iconic "magic loogie theory" scene from the season 3 episode of Seinfeld is a parody of a 1991 movie which explores the incidents surrounding the death of a US President. Name the American President.

"The Contest”, the season 4 episode which won Primetime Emmy Award for Outstanding Individual Achievement in Writing in a Comedy Series, served as the main source of inspiration for a 2020 reality television show on Netflix. Name the show.

This recurring character in the series is a parody on the famous American lawyer Johnnie Lee Cochran Jr. He appears in the series' from the seventh to ninth seasons as Cosmo Kramer's lawyer. Name the character.

Which former Mayor of New York City made a cameo appearance as himself in the Seinfeld episode "The Non-Fat Yogurt", which is a fictionalised account of the 1993 mayoral election?