((He was cast as Marty McFly in Back to the Future (1985) after Robert Zemeckis and Bob Gale were unable to get Michael J. Fox, the first choice for the part due to scheduling conflicts. After filming for six weeks, he was let go from the film because Zemeckis and Gale felt he was "too intense" for the character. Michael J. Fox was then available and he took over the part.))
Eric Stoltz originally played the character of Marty from the great 80s movie Back to the Future. From the looks of the pictures, it seems they filmed a great deal of the movie before he was replaced. They then had to re-shoot everything with Stoltz in it.
Again check out all the pics here