<Tr> <Th> Occupation </Th> <Td> Actor </Td> </Tr> <Tr> <Th> Years active </Th> <Td> 1987--present </Td> </Tr> <P> John Mark Galecki (born April 30, 1975) 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). </P> <P> Galecki is one of the highest paid television actors in the world, with his role in The Big Bang Theory currently earning him approximately US $900,000 per episode between 2017 and 2019 . </P>

The guy who plays leonard on big bang theory