12. Michael J. Fox: Then
When Fox filmed BTTF, as you already know he was still on the set of Family Ties. The shuttling back and forth allotted the young actor about four hours of sleep per night. The lack of sleep undermined Fox’s confidence in his performance. “I thought I sucked in it,” he told Parade magazine in 2012. “I really, truly thought I was terrible. So many times I was practically unconscious because I was so tired.” What a pleasant surprise when the movie became the blockbuster hit of the summer.