Johnny Galecki, who played Leonard Hofstadter in The Big Bang Theory, was initially offered the role of Sheldon Cooper by creator Chuck Lorre. However, Galecki turned it down and opted to play Leonard instead. He wanted to explore the character's romantic life, something he had not done before. Jim Parsons auditioned for the role of Sheldon and blew the creators away with his performance. Although Chuck Lorre had doubts about Parsons being able to deliver the same level of performance consistently, Bill Prady invited him back for a second audition, which confirmed that Parsons was perfect for the role.
