Back to the Future (partially found Eric Stoltz performance as Marty McFly footage of science-fiction film; 1985)
In preparation for filming the 1985 science fiction comedy Back to the Future, director Robert Zemeckis and producer Bob Gale wished to cast Michael J. Fox in the lead role of Marty McFly but were unable to due to Fox's commitment to the TV sitcom, Family Ties.
Therefore, at a studio executive's insistence, actor Eric Stoltz was cast instead. However, after filming roughly five weeks of footage with him, Zemeckis felt that Stoltz wasn't playing the type of comedy that the part required and fired him. By that time, Fox had become available again, and filming resumed with him in the role.
The footage of Stoltz's performance as a whole has never been released, although many photographs and a couple brief dialogue-less clips have surfaced. One of the film's writers, Bob Gale, has also stated that the footage still exists and may one day be released. In addition, the scene where Marty punches Biff in the 1950s cafe uses footage from Stoltz's performance but this was debunked by the film's editor Harry Keramidas in an interview for the Netflix docuseries The Movies that Made Us he debunked it stating that the scene was reshoot and that the person playing Marty was most likely a stunt double. 
In 2010, for the 25th-anniversary release of the film on Blu-ray and DVD, several silent fragments of Stoltz playing Marty were included as part of a new documentary about the first film on the discs.
In a 2008 interview with The Opie and Anthony radio show, Bob Gale stated that Eric's scenes would not be released due to them not wanting to "embarrass him" with the footage.
In the 2015 documentary Back In Time, Zemeckis revealed that the tapes containing Eric as Marty were not destroyed, and he plans for the whole footage to be released in the future.
- Article stating Eric Stoltz's footage still exists and may one day be released. Retrieved 10 Jan '18
- Article on Stoltz's footage staying in the film. Retrieved 10 Jan '18