Before Michael J. F ox got the job on Back to the Future, Eric Stoltz was in the role of Marty McFly. He shot five weeks in that role, and ended up being fired.
The video has director Robert Zemeckis and Steven Spielberg talking about the decision on why they decided to get Michael J. Fox. Hope this is on the future bluray release of the Back to the Future trilogy.
Click HERE for the video.