who plays zach in the big bang theory
Brian Thomas Smith 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.
Johnny Galecki John Mark Galecki (born April 30, 1975)[1] is an American actor. He is known for playing Leonard Hofstadter in the CBS sitcom The Big Bang Theory (2007–present) and David Healy in the ABC sitcom Roseanne (1992–1997; 2018). Galecki also appeared in the films National Lampoon's Christmas Vacation (1989), Prancer (1989), Suicide Kings (1997), I Know What You Did Last Summer (1997), Bookies (2003), In Time (2011), and Rings (2017).