Jason Alexander: Jason Alexander. Actor: Seinfeld. Jay Scott Greenspan, known professionally as Jason Alexander, is an American actor, comedian, film director, and television presenter. An Emmy and Tony winner, he is best known for his role as George Costanza in the television series Seinfeld (1989), for which he was nominated for seven consecutive Primetime Emmy Awards and four Golden Globe Awards. His other well-known roles include Phillip Stuckey in the film Pretty...
