Fritzo
Lifer
Michael J Fox was the first choice to play Marty McFly in Back to the Future, but he was too busy working on the TV series Family Ties. Therefore, the producers cast Eric Stoltz (he played on movies like Mask and Some Kind of Wonderful). After 4 weeks of shooting, Stoltz got the boot because he was playing the role too seriously (he wanted to make it an action movie, not a action/comedy like intented). Luckily, by this time, Fox had become available.