Jason Alexander (born "Jay Greenspan", September 23, 1959, in Newark, New Jersey) was one of the stars of the award-winning television sitcom "Seinfeld". His character, the neurotic ne'er-do-well George Costanza, Jerry Seinfeld's best friend, was based in part on the show's creator, Larry David. He has also appeared in a number of movies, and done some work as a director including a recent successful Hollywood concert version of the musical Hair for which he was also the emcee.
Alexander has also done a McDonalds commercial advertising the McDLT a sandwich that separated the beef "hot side" from the rest of the hamburger "cool side". The commercial features the singing talents of Alexander.