<P> Galecki made his acting debut in the 1987 CBS miniseries Murder Ordained with JoBeth Williams and future Roseanne co-star John Goodman . In 1989 , Galecki portrayed Rusty Griswold in National Lampoon 's Christmas Vacation . In 1990 , he was cast as Danny Nash , the son of Robert Urich 's lead character , on the NBC comedy American Dreamer ; the following season , he was a regular cast member on the ABC sitcom Billy , a spin - off from Head of the Class . He appeared in one episode of Blossom in 1991 , opposite his future The Big Bang Theory co-star Mayim Bialik . </P>
<P> Galecki made his acting debut in the 1987 CBS miniseries Murder Ordained with JoBeth Williams and future Roseanne co-star John Goodman . In 1989 , Galecki portrayed Rusty Griswold in National Lampoon 's Christmas Vacation . In 1990 , he was cast as Danny Nash , the son of Robert Urich 's lead character , on the NBC comedy American Dreamer ; the following season , he was a regular cast member on the ABC sitcom Billy , a spin - off from Head of the Class . He appeared in one episode of Blossom in 1991 , opposite his future The Big Bang Theory co-star Mayim Bialik . </P>
what part did johnny galecki play in christmas vacation
what part did johnny galecki play in christmas vacation
Rusty Griswold
Rusty Griswold