Although born in Belgium, Johnny Galecki and his two siblings grew up in Illinois. He dropped out of school in 8th grade and made his acting debut in the 187 miniseries Murder Ordained. Two years later, he landed a part in National Lampoon’s Christmas Vacation, followed by American Dreamer and Billy. While on the ABC sitcom, he began a recurring role on Roseanne as David. He became a main cast member in 1992 and remained there until its end in1997. He also returned for the revival series in 2018. After starring in multiple movies, he landed his breakthrough role on The Big Bang Theory, which aired from 2007 to 2019.
Galecki dated his Big Bang Theory costar (and his character’s main love interest) Kaley Cuoco, from 2007 to 2009. After the split, the pair remained best friends. He went on to date Alaina Meyer from 2018 to 2020, when they split. The pair welcomed a child together in December 2019.