Eric Stoltz in ‘Back to the Future’ — Before Michael J. Fox Replaced Him (Video)

Spielberg, Zemeckis reveal clip of actor they initially had in "Marty McFly" role

The 25th anniversary edition of 1985's "Back to the Future" will be released later this month on Blu-Ray.

Included in the package is a never-before-seen clip of Eric Stoltz, the actor who had cast as "Marty McFly" before executive producer Steven Spielberg and director Robert Zemeckis decided to replace him with Michael J. Fox — which, for Fox, turned out to be a career-defining role.

Zemeckis called Stoltz a "magnificent actor," but his comedic sensibilities didn't match up with the script he'd written. "I don't think we were getting the laughs we thought we would get," Spielberg said.

Shockingly, Stoltz was replaced with Fox five weeks into filming, and Zemeckis had to convince the studio to let him reshoot.

"I had to make this horrific decision," Zemeckis said, despite the resulting classic film, "which was heartbreaking for everybody, but luckily I was able to convince the studio to let me reshoot five weeks of work."