The process of filling a movie with a group of talented thespians is a rather simple one when you break it down. Look at the part you need to fill, see which actors are currently available that fit the bill, convince them (or pay them enough money) to sign on the dotted line, and away you go.
Yet, if this thing called life has taught us one thing, it's that even the simplest of scenarios have the potential to go sideways in next to no time. So, when the aforementioned casting of an actor is abruptly combined with the variables of either a sudden death, breakdown of a relationship, or even just a change of heart, creative ways of papering over the crack often come to light.
Either through the use of some crafty make-up and prosthetics, some deceptively similar stand-ins, or some long forgotten recycled footage from the past, these movies tried their very best to pull the wool over our eyes and have us believe that certain actors were present on set during the shooting of the films in question.
This is why people have trust issues.
10. Gene Hackman - Superman II
After the unquestionable success of Richard Donner's first Superman flick back in 1978, it was safe to assume that the director would be given the freedom to take the series in whatever direction he pleased following a not too shabby $300 million haul at the box office.
However, around three quarters of the way through shooting Superman II, Donner eventually decided that enough was enough after butting heads with producers Ilya and Alexander Salkind over the sequel's overall budget. He was then replaced by Richard Lester, but this didn't exactly go down well with the rest of the cast.
In particular, Gene Hackman was less than impressed by the treatment of Donner. So, when the time came to reshoot certain parts of the movie, the Lex Luthor actor outright refused to play ball. This forced Lester to think on his feet to ensure one of the series' key players still played a significant part in the movie.
In the end, body doubles and voice impersonators were used to trick audiences into thinking they were actually watching Hackman on screen at various points in the flick, when in reality the actor was likely just chilling on a beach somewhere.