Michael J. Fox was Robert Zemeckis and Bob Gale's first choice to play Marty McFly, but Fox's commitments to the hit television series Family Ties made him unavailable. Although other young actors were considered, Universal executive Sidney Sheinberg strongly preferred Eric Stoltz, whose dramatic performance in the then-unreleased Mask had impressed him. Zemeckis accepted Stoltz on the understanding that the production could be reshot if the casting failed, and principal photography began in November 1984 with Stoltz in the lead.
Within weeks, Zemeckis concluded that Stoltz was not right for the film's comic tone and timing. Stoltz reportedly approached Marty as a more serious dramatic character, while the filmmakers wanted the awkward, quick-witted energy they believed Fox could bring from Family Ties. The studio then negotiated an unusual arrangement allowing Fox to work on both productions, forcing the Back to the Future crew to film around his television schedule. Scenes already completed with Stoltz had to be discarded and filmed again with Fox, adding approximately $4 million to the budget and extending the pressure on the production. The gamble transformed the film, but it also left Stoltz's work largely unseen and became one of the most consequential lead-actor substitutions in modern blockbuster history.
