Train trip to San Francisco takes a major detour when Sheldon discovers he forgot his flash drive and Leonard, Wolowitz and Raj discover that sci-fi actor Summer Glau is onboard.
Guest Cast
Robert Clotworthy
voices ConductorCast Appearances
Kaley Cuoco
as Penny
Episode Discussion
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From archived tv.com trivia: A fan of the show's often physics-centric humor, Nobel Laureate Dr. George Smooth contacted the show and was subsequently found a role as himself in this episode. Smoot won the Nobel Prize in Physics for his work on the Big Bang Theory of the universe using the Cosmic Background Explorer Satellite.