You can have the best script and the best director and the best special effects — heck, you can even have a time-traveling DeLorean — but if you don’t have the right chemistry between actors, then you have nothing. This fact of filmmaking was proven in the casting for Back to the Future.

Eric Stolz was originally cast as Marty McFly when first choice Michael J. Fox was unavailable due to his shooting schedule on Family Ties. But on Jan. 10, 1985, after about six weeks of filming, the actor was fired due to his style being deemed too intense and not comedic nor manic enough. An arrangement was then made to bring Fox aboard even as he continued to film Family Ties.

It was a gutsy — and expensive — move to replace the lead actor of the movie and reshoot all that footage, but it proved to be one of the smartest decisions in Hollywood history. And, as a new featurette on the Back to the Future: The Ultimate Trilogy 35th anniversary set (out Oct. 20 on 4K, Blu-ray, and digital) shows, the addition of Fox made the key relationship between Fox’s Marty McFly and Christopher Lloyd’s Doc Brown sing.

Credit: Ralph Nelson/Universal

“One of the things that people loved so much about Back to the Future and the sequels is the relationship between Marty and Doc,” says BTTF producer and co-writer Bob Gale in the featurette. “Michael J. Fox and Christopher Lloyd hit it off brilliantly.”

According to Gale, that connection was not necessarily a given because the two actors had very different styles and methods of preparation. “It was very unusual because Christopher is a theatrically trained actor,” explains Gale. “He knew every line of the script on the first day of shooting. Michael was trained on Family Ties, a sitcom, so Michael never learned his lines until about 10 or 15 minutes before we were going to shoot the scene.”

Fox’s last-minute line-learning also worked its way into the final film. “Michael would throw Chris for a loop by saying something that wasn’t originally in the script,” recalls Gale. “Chris was such a good actor that he just went with it and made something out of it. These guys became great friends. Still are great friends.”

And they made a great pair on screen. To watch the exclusive clip of Gale discussing the working relationship between the actors and their iconic roles, check out the video at the top of the post. And for more, pick up the Back to the Future: The Ultimate Trilogy 35th anniversary set out on Oct. 20.

Video courtesy of Universal Pictures Home Entertainment.

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