Kevin Sussman (born December 4, 1970) is an American actor of television and film perhaps best known for his recurring roles as Stuart Bloom on The Big Bang Theory and as "Walter" on the now defunct comedy-drama Ugly Betty. Kevin has been promoted to series regular on CBS sitcom The Big Bang Theory starting from the sixth season. While he was demoted back to recurring guest during the end of the sixth season, he was promoted to series regular again starting with the eight season. Besides the main couple and Raj, he has had the most appearances on the show of everyone else.