John Mark 'Johnny' Galecki (born April 30, 1975) is an American actor.He is best known for his roles as David Healy in the ABC sitcom Roseanne, Rusty Griswold in National Lampoon's Christmas Vacation, and as Leonard Hofstadter in the CBS sitcom The Big Bang Theory. Galecki was born in Bree, Belgium, of Polish, Irish, and Italian descent. His mother, Mary Lou, was a mortgage consultant, and his father, Richard Galecki, was a member of the U.S.Air Force stationed in Belgium and also worked as a rehabilitation teacher. He has a younger brother, Nick, and a younger sister, Allison. Galecki moved to Oak Park, Illinois, with his family when he was three years old. This book is your ultimate resource for Johnny Galecki. Here you will find the most up-to-date information, photos, and much more. In easy to read chapters, with extensive references and links to get you to know all there is to know about his Early life, Career and Personal life right away. A quick look inside: Johnny Galecki, Murder Ordained, A Night in the Life of Jimmy Reardon, National Lampoon's Christmas Vacation, Blind Faith (1990 film), A Family Torn Apart, Without Consent, Bean (film), Suicide Kings, I Know What You Did Last Summer, The Opposite of Sex, Playing Mona Lisa, Bounce (film), Morgan's Ferry, Vanilla Sky, Bookies (film), Table for Three, In Time, American Dreamer (TV series), Billy (1992 TV series), Roseanne (TV series), The Big Bang Theory.