<Tr> <Th> </Th> <Td> (1977 - 05 - 13) May 13, 1977 (age 41) St. Louis, Missouri, US </Td> </Tr> <Tr> <Th> Occupation </Th> <Td> Actor Comedian Producer </Td> </Tr> <P> Brian Thomas Smith (born May 13, 1977) is an American actor and comedian known for playing the dim - witted but kind - hearted Zack Johnson on The Big Bang Theory, and his appearances on Fear Factor and The Amazing Race Season 7 . He has also made guest appearances on Two and a Half Men and The 100 Greatest TV Quotes & Catchphrases . </P> <P> Brian Thomas Smith has a younger brother, Greg, who participated with him on The Amazing Race . </P>

Who plays zach in the big bang theory