Kevin Sussman, who plays Stuart - the owner of the Pasadena Comic Center, which the gang frequent - has been promoted to a series regular for the sixth season of The Big Bang Theory.
Sussman, who has so far appeared in fifteen episodes of the show, will not necessarily appear in every episode of the season like the main cast members. He will reportedly be appearing in somewhere around 7-13 episodes this season. His new contract guarantees his availability to the show as he's required.
Sussman is the fourth recurring guest star to have been bumped to regular. Sara Gilbert, who played Leslie Winkle, was made a regular for Season 2 but later left the show. Melissa Rauch and Mayim Bialik, who play Bernadette and Amy respectively, were promoted to regulars during Season 4 and remain main cast members to this day.
This story was originally published on The Big Bang Theory Site.