Season 6 premiered on September 27th, 2012, and ended on May 16, 2013. All of the seven regular actors on the show returned to their respective roles. The first episode taping began on August 14, 2012. It was announced that starting from this season, Kevin Sussman, who plays Stuart Bloom, would be a regular, though he is later demoted back to recurring. Starting with Howard’s trip to the International Space Station, Penny is pushed deeper into her relationship with Leonard when Sheldon’s graduate assistant Alex Jensen is interested in Leonard. The season ends with Leonard leaving for the North Sea to help Stephen Hawking prove a theory, and Raj undergoing a major social transition.