caption birth_place nationality birth_date yearsactive birthname image article_title occupation
galecki at paleyfest 2013 bree , belgium american 30 april 1975 1987 -- present john mark galecki johnny galecki at paleyfest 2013.jpg johnny galecki
 actor
johnny galecki

john mark `` johnny '' galecki -lrb- born april 30 , 1975 -rrb- is an american actor .
he is known for his role as david healy in `` roseanne '' from 1992 -- 97 and as dr. leonard hofstadter in `` the big bang theory '' since 2007 .
galecki also appeared in the films `` national lampoon 's christmas vacation '' -lrb- 1989 -rrb- , `` suicide kings '' -lrb- 1997 -rrb- , `` i know what you did last summer '' -lrb- 1997 -rrb- , `` bookies '' -lrb- 2003 -rrb- , `` hancock '' -lrb- 2008 -rrb- , and `` in time '' -lrb- 2011 -rrb- .
