Michael J. Fox Remembers ‘Nothing’ of Final Day Filming ‘Back to the Future’ 40 Years Later

Michael J. Fox opened up about filming Back to the Future, describing his exhaustion after simultaneously starring in his hit sitcom, Family Ties, in his new book, Future Boy.

Fox, 64, recalled the final week of filming the 1985 classic, writing, "Over the previous week, the rest of the cast had one-by-one wrapped their final scenes and signed out. It came down to me, Zemeckis, Gale and a skeleton crew in the farmlands near Chino, California."

He continued, "After 3 and a half months of filming Back to the Future, 40 days of which was also spent taping Family Ties, this was the end."

Fox was the star of Family Ties, filming 20-plus episodes a season, when he was tapped to replace Eric Stoltz as Marty McFly.

"Let me tell you what I remember about that last day: I don’t remember anything. Nothing. Nada. Zero. Bupkis," Fox wrote in the memoir, explaining that he tapped Bob Gale for help jogging his memory. "By the time we wrapped, I was too exhausted to search for indicators of greatness. I had other things on my mind."

He explained his routine during the three months of filming the time-travel movie, writing, "[the schedule] left little time to be me.”

"I was Alex, I was Marty, and I was Mike. That’s two too many. In order to complete my work, at least one of them had to go, and Mike was the odd man out," he wrote.

From 9 a.m. to 5 p.m. he was on set of Family Ties. After wrapping, "I grab something to eat in my dressing room, tuck my Back to the Future script under my arm, and by 5:15, I’m in the teamster-driven station wagon, headed to Universal."

He recalled memorizing lines while en route to the film set.

"Somewhere over the Cahuenga Pass, I manage to push Alex’s voice out of my head and tune in Marty — his cadences, his incredulous crackle."

He would then wrap filming around 2:30 a.m. and have to be awake again by 7 a.m. to "absorb" the new script for Family Ties.

According to the Spin City star, he had "no idea" the film would become an American classic.

"I can honestly say I had no idea what all this added up to; that is, I had not seen one bit of dailies or any edited footage," he wrote. he writes of the end of filming.

Back to the Future turned 40 earlier this year, and fans can celebrate by getting their hands on some limited-edition merch, including Fisher-Price Little People Collectibles, head to theaters to see their favorite film as it returns to the big screen, and check out Fox's newest book.