Michael J. Fox is revealing what really went on behind the scenes of the iconic ’80s franchise Back to the Future and a hidden feud with one particular co-star.

In Fox’s new memoir, Future Boy: Back to the Future and My Journey Through the Space-Time Continuum, the actor detailed issues his co-star Crispin Glover faced on-set and was said to have “created friction” with his acting style. Fox wrote, “Nobody puts Crispin in a box. But that didn’t prevent the camera crew from literally building a box around him.”

Fox starred alongside Glover in the 1985 movie Back to the Future, and it’s officially been 40 years since the classic film’s release. Back to the Future follows a weird scientist, Doc (played by Christopher Lloyd), as he begins an experiment and enlists the help of teenage Marty McFly (played by Fox). They must go back in time and fix the mess they made.

According to Fox, Glover had “his own ideas as to how and where” his character Marty McFly’s dad George should move. Fox continued by adding:

“As Crispin approached the camera, he was meant to stay in a lane between the clothesline and me. But Crispin had a different plan. My guess is that he saw George as a wanderer, a free spirit who traveled in random patterns – in this case, perpendicular to the camera.”

Despite the crew’s “feud” with Glover, Fox insists he loved working with his on-screen father and even says, “His talent was unquestionable, although his methods sometimes created friction. Still, I respected how he remained true to George (as he understood and embodied him).“

Fox recalls meeting Glover before being together on Back to the Future. “I knew Crispin Glover prior to Back to the Future. I wouldn’t, however, say I was prepared to act with him – there’s no way to prepare for Crispin.”

In Future Boy, Fox also recalls an incident with Eric Stoltz, as Fox famously replaced the fellow actor as Marty McFly. The two actors remained friends, and Fox insists there’s no bad blood between them both.

Fox was an iconic actor during the ‘80s and ‘90s and has been battling Parkinson’s disease since 1991. He is also known for his roles in Family Ties, Stuart Little, and Teen Wolf.

The Back to the Future franchise still remains a favorite for fans, young and old, and the first film has an impressive Rotten Tomatoes score of 93%. The franchise features three films and collectively grossed over $960 million at the box office, with the first movie earning $389 million globally.