Brian Smith (born May 13, 1977, St. Louis, Missouri) is an actor and reality TV star. Brian has seventy-three credits as of August, 2013, including regular roles in the series The Flip Side, Suit Up, Wolfpack of Reseda, Casual: The Series, The Big Bang Theory and A Good Knight's Quest. In 2005, Brian and his younger brother, Greg Smith, were teamed in The Amazing Race, season 7. He has portrayed Penny's dim witted friend and sometimes boyfriend Zack Johnson. He has also been a member of the sketch comedy troupe "The Exploding Pajamas". He appeared again on TBBT in 2013 as Penny's accidental husband.
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