Born and sometimes credited as Jason Greenspan, the actor best 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. This performer changed his named to Jason Alexander in high school and began working professionally in films and on Broadway not long after graduating. The new surname itself was a great help in landing parts, since auditions were inevitably conducted in alphabetical order. Alexander does actually have a musical bac...