Jason Alexander (born September 23, 1959) is an American actor, comedian and singer, best known for his role as George Costanza on the television series Seinfeld. Born and sometimes credited as Jason Greenspan, the actor known as one of Seinfeld's idiot friends during the '90s has an original soundtrack discography that includes one of composer Stephen Sondheim's biggest flops, the early '80s show Merrily We Roll Along.

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