It's hard to imagine famous movies separate from their casts - once film and film actor have been brought together and melded into a single finished product, it's near impossible to think of them without one another, which makes sense, given that - as audiences - we're only really ever treated to one version of a movie. This isn't like theatre, where you can watch the same play or show with different actors in the leading roles, and decide which ones were better suited to each part every time you see a new performance: a movie generally only gets one go around. As a result, it's easy to forget that - once upon a time - all movies were just words on paper, and that casting possibilities were totally and utterly endless. Any actor could have ended up nabbing any role, given the right circumstances. So although some actors originally thought right for certain famous roles and later denied the parts might've actually done a good job, there are other original casting choices that seem kind of insane in retrospect. Here are 10 of that kind, all of which would have probably ruined the associated movies had these actors actually been cast...