John Mark Galecki (born April 30, 1975) is an American actor. He is known for playing Leonard Hofstadter in the CBS sitcom The Big Bang Theory (2007–present) and David Healy in the ABC sitcom Roseanne (1992–1997; 2018). Galecki also appeared in the films National Lampoon\'s Christmas Vacation (1989), Prancer (1989), Suicide Kings (1997), I Know What You Did Last Summer (1997), Bookies (2003), In Time (2011), and Rings (2017). \n', '

Galecki is one of the highest paid television actors in the world, with his role in The Big Bang Theory currently earning him approximately US$900,000 per episode between 2017 and 2019.\n', '

Galecki was born in Bree, Belgium, to American parents of Polish, Irish, and Italian descent. His mother, Mary Louise (Mary Lou) Noon, was a mortgage consultant, and his father, Richard Galecki, was a member of the U.S. Air Force stationed in Belgium, and also worked as a rehabilitation teacher. Galecki is the eldest of three children with a brother, Nick, whom he describes as a "mechanical genius" in the automotive industry, and a sister, Allison. Galecki grew up in Oak Park, Illinois.\n', '

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