It’s quite common for a movie production to replace an already cast actor before filming starts…but quite uncommon (and expensive) to replace a star after the cameras have started rolling.
Director Robert Zemeckis’ first choice for Marty McFly in Back to the Future: Michael J. Fox, who was unavailable due to a long shooting schedule for his TV show, Family Ties. Eric Stoltz was cast in the role instead, but after filming for a few weeks, it became clear that Stoltz wasn’t working out—mainly that the serious, highly trained actor wasn’t playing Marty as a comic character. Stoltz was fired, and Fox found a hole in his schedule, and he was cast. (Stoltz scenes were re-shot with Fox.)
Harvey Keitel had filmed roughly 90 percent of his scenes for Stanley Kubrick’s final film, Eyes Wide Shut. Kubrick was a demanding director, and months after the initial shoot called Keitel back to the set to reshoot almost all of this finished scenes. By that time Keitel was busy on another movie, requiring Kubrick to reshoot all of Keitel’s work with Sydney Pollock.
About a quarter of the way through production on There Will Be Blood, director Paul Thomas Anderson abruptly decided to recast the role of Eli Sunday, preacher and rival to oilman Daniel Plainview (Daniel Day-Lewis). Actor Kel O’Neill was reportedly too intimidated by Day-Lewis, and was replaced with Paul Dano, who was already in the movie, portraying the brother of O’Neill’s character.
What movie was Chris Farley working on when he died in 1997? An animated movie about an ogre called Shrek. He’d recorded about three-fourths of the movie, and the production was delayed until filmmakers found a replacement: Farley’s Saturday Night Live castmate Mike Myers. Myers re-recorded the dialogue, but he thought it would be funnier if Shrek had a Scottish accent. That required animators to edit the footage already shot to match Myers’ new lip movements at a cost of $5 million.