With Eric Stoltz out and Michael J. Fox in, the stress on Back to the Future director Robert Zemeckis was immense. He had staked his directing career on this film and his reputation on the change from Eric to Michael. On the outside, the film sounded like it would be a mess. Every studio rejected it; Columbia Pictures only bought the script to get Zemeckis to do something else for them. In the beginning, Universal Pictures was only doing it as a very expensive favor to Steven Spielberg, who it wanted to keep happy. With a major recast, ballooning budget and possibly catastrophic delays, there were few outside of Amblin Entertainment who expected much from the film.
Production, however, moved forward. Michael J. Fox would spend the day at Paramount, working on Family Ties then heading out to Universal for Back to the Future. He now describes that time period as a rough one, getting as much sleep as he could in between makeup and costuming changes. By day he was Alex P. Keaton. By night, Marty McFly.
Once the grueling shoot ended, a rush was put on finishing the post-production special effects. Universal Pictures had posted a billboard near its famed studio that counted down the days until Back to the Future would be unleashed in theaters. The ironic thing about the billboard was that the film was not yet finished when it was erected. Cast and crew were regularly driving past the billboard to get to work each day, so the billboard not only promoted the film to potential ticket buyers, it was a stark reminder to everyone involved in the film’s production that they were almost running outta time.