Only three people know for sure the exact timeline of events that led to Brad Pitt and Jennifer Aniston getting divorced and Brad Pitt and Angelina Jolie getting together. The official demise of one relationship and beginning of another is something that really should only be the business of the parties involved. Unfortunately for Pitt, Aniston, and Jolie, however, we have Mr. & Mrs. Smith.It’s hard to imagine a reality in which Pitt and Jolie never got together after meeting on the set of the 2005 movie, in which they played married assassins and displayed some of the most smoking-hot chemistry in the history of the moving image. But guess what? We almost didn’t have Brangelina, because Pitt and Jolie weren’t the original stars of Mr. & Mrs. Smith. That’s how much the casting of a film can alter people’s destinies. Also, can you imagine anyone else bringing such über-cool to John and Jane Smith?Mr. & Mrs. Smith isn’t the only film to undergo a reshuffling that changed everything. In fact, there's a movie that underwent one helluva nightmarish production before finally getting released last Friday: Jane Got a Gun , a Western starring and produced by Natalie Portman.The original director, Lynne Ramsay, never showed up to the first day of shooting. Her lack of confidence in the project led to stars Bradley Cooper and Jude Law exiting, as well. Cooper and Law were replaced by Joel Edgerton (who also co-wrote the film) and Ewan McGregor. Gavin O'Connor stepped in to direct, but one can’t help but wonder how the movie would have turned out with the original trio of Portman, Cooper, and Law. Actually, Michael Fassbender was set to play Jane’s (Portman) husband before Cooper and Law were brought on, but he had to depart to shoot X-Men: Days of Future Past. So add Michael Fassbender into the mix of what might have been.Some of your favorite movies of all time were almost completely different. They would have been unrecognizable if they’d been made with the original cast members. Get ready to have your mind blown when you realize which iconic roles were actually late-in-the-game replacements.