Before The Big Bang Theory, Johnny Galecki Starred In A Spin-Off Of A Classic '80s Sitcom

Johnny Galecki had a long, established acting career behind him when he joined "The Big Bang Theory." He got his start as a child actor, and the role he took on just before he became a household name stemmed from a successful '80s sitcom — "Head of the Class." When that classic ended after five seasons, one-season wonder teacher Billy MacGregor (played by actor Billy Connolly) spun off into his own solo sitcom called "Billy." In it, MacGregor moves on from educating high school kids and switches coasts — heading to California from New York. The Scottish man gets a job at a community college, where he finds his work permit has expired, threatening his citizenship status. He enters into an in-name only green card marriage with Mary (actor Marie Marshall), a divorcee who happens to have an illegally-built spare room for him to use and a big mortgage to pay off. Galecki plays the eldest of Mary's three children — the rebellious David.

"Billy" lasted for only 13 episodes before the ABC network pulled the plug. Its cast would quickly scatter to the wind. But the death of "Billy" resulted in a major boon for Galecki — who would soon find himself happily ensconced in the bosom of another sitcom clan.

Johnny Galecki's career quickly rebounded after "Billy" was cancelled. While that show was still airing its last episodes, the actor began a long run on another ABC series, "Roseanne." Galecki already had a connection to one of its cast members; he appeared in the now-forgotten movie "Backfield in Motion" with Roseanne Barr in 1991. Galecki joined "Roseanne" during Season 4 as nebbish David Healy, who would quickly become the boyfriend of Darlene Conner (played by Sara Gilbert) and eventually her husband. Darlene and David would have two children together before divorcing, and Galecki would pop in and out of the revival seasons of "Roseanne" and "The Conners" for years, even while "The Big Bang Theory" was airing. "The Conners" even formulated a backup plan if Galecki didn't return for a cameo, showing just how important he'd become to the show's history.

Years later, his time on "The Big Bang Theory" would only add to his legacy, cementing his status as a comedy great. Sara Gilbert eventually joined Galecki on the series as well, further solidifying their connection in popular memory. That just goes to show that sometimes when a door closes, a window opens — and "Billy" proved to be Galecki's closed door.