National Lampoon's Christmas Vacation is a film that stars an actor known for playing Dr. Leonard Hofstadter in what CBS sitcom?
National Lampoon's Christmas Vacation:  The film stars Chevy Chase, Beverly D'Angelo and Randy Quaid, with Juliette Lewis and Johnny Galecki as the Griswold children Audrey and Rusty, respectively. Johnny Galecki:  He is known for playing David Healy in the ABC sitcom "Roseanne" from 1992 to 1997 and Dr. Leonard Hofstadter in the CBS sitcom "The Big Bang Theory" since 2007.
i don't know