Dr. Leonard Hofstadter (played by Johnny Galecki) got his first real big break in the classic National Lampoon's Christmas Vacation film with Chevy Chase as Rusty Griswold. http://bigbangtheorytribe.com/?p=3406
Johnny Galecki (l.) and Juliette Lewis (r.) were child stars in the Christmas classic, "National Lampoon's Christmas Vacation." Galecki played son Rusty while Lewis played daughter Audrey in the National Lampoon Christmas themed movie. Galecki is best known for his current role as Dr. Leonard Hofstadter in the CBS hit comedy "The Big Bang Theory." Galecki is also known for his role in the sitcom "Roseanne" and slasher "I Know What You Did Last Summer." Lewis is best known for her roles in…
Amazon.com: National Lampoon's Christmas Vacation [Blu-ray]: Chevy Chase, Beverly D'Angelo, Cody Burger, Tony Epper, Miriam Flynn, Alexander Folk, Johnny Galecki, Nicholas Guest, William Hickey, Diane Ladd, Ellen Hamilton Latzen, Juliette Lewis, Julia Louis-Dreyfus, Keith MacKechnie, E.G. Marshall, Sam McMurray, Natalia Nogulich, Randy Quaid, Mae Questel, John Randolph, Thomas E. Ackerman, Angelo Badalamenti: Movies & TV
Johnny Galecki: Then Before finding his inner geek on The Big Bang Theory, Galecki was best known for playing David Healy on Roseanne. But he also had roles in some other 1980s and '90s classics. In 1989, at age 14, he starred as Rusty Griswold in National Lampoon's Christmas Vacation, alongside Chevy Chase, Beverly D'Angelo, and Juliette Lewis.