Johnny Galecki turns 38 today!
The actor had a memorable turn in "National Lampoon's Christmas Vacation," before embarking on a TV career that's last over 20 years.
And while he's now known for playing Leonard Hofstadter on "The Big Bang Theory" (after originally being asked to play Sheldon Cooper), his big break came as Darlene's (Sara Gilbert's) boyfriend David on "Roseanne."
And while Johnny looks pretty much like he did during his "Roseanne" days, the same can't be said for the rest of the cast. Click on the "Launch Gallery" link above to see what his sitcom family looks like today.