| First Name | Johnny |
| Middle Name | Mark |
| Last Name | Galecki |
| Full Name at Birth | John Mark Galecki |
| Age | 36 |
| Date of Birth | April 30, 1975 |
| Birthplace | Bree, Belgium |
| Height | 5' 5" (165 cm) |
| Build | Average |
| Eye Color | Brown - Light |
| Hair Color | Brown - Dark |
| Distinctive Features | Short statureExpressive eyebrows |
| Star Sign | Taurus |
| Ethnicity | White |
| Nationality | American |
| Occupation Category | Actor |
| Claim to Fame | Rusty Griswold in National Lampoon's Christmas Vacation, David Healy in the U.S. sitcom Roseanne, Leonard Hofstadter On The Big Bang Theory |
| Shoe Size | 8.5 |
| Father | Richard Galecki (member of U.S. Air Force) (deceased) |
| Mother | Mary Lou Galecki (realtor) |
| Brother(s) | Nick Galecki (younger) (car collision consultant) |
| Sister(s) | Allison Galecki (younger) (aesthetician) |
| Pets | Vera (dog - boxer mix) |
John Mark "Johnny" Galecki (born April 30, 1975) is a Belgian-born American actor. He is best known for his roles as David Healy in the sitcom Roseanne, Rusty Griswold in National Lampoon's Christmas Vacation, and as Leonard Hofstadter, PhD, in the CBS sitcom The Big Bang Theory.
Selected Johnny Galecki film and TV show credits: