Despite the fact that The Big Bang Theory concluded its impressive 12-season run years ago, fans remain captivated by the show. Over the years, intriguing behind-the-scenes details have emerged, with one particularly fascinating revelation being the challenges of casting Johnny Galecki. Surprisingly, Galecki resisted taking on the roles of both Sheldon and Leonard multiple times. So, what exactly led the Roseanne star to reject such an iconic character? The answer lies in Galecki's struggle to grasp the show's vision and his reluctance to leave his life in New York for a sitcom with unclear potential.