Johnny Galecki (b. 1975) is an American actor known for playing Leonard Hofstadter on The Big Bang Theory (with Jim Parsons) and David Healy on Roseanne. He also played Rusty Griswold in National Lampoon's Christmas Vacation.
Galecki appeared in a Season 42 segment of Sesame Street; where he explained the Word of the Day "transform" with Abby Cadabby, only to be magically transformed into a Muppet pumpkin.