Many actors have an iconic character that defines their movie career. Mention their name in a conversation and the name and image associated with that character immediately spring to mind. It is difficult to picture anyone else filling that role. In reality, several of those actors were not the original choice for that part.

If not for a few twists of fate, these eight classic characters would have been brought to life by a different actor:

Indiana Jones: Playing a globe-trotting archeologist who tangles with Nazis and other villains to obtain mystical artifacts turned Harrison Ford into an action superstar after his earlier turn as Han Solo in "Star Wars." Ford was a last minute replacement after Tom Selleck was forced to turn down the role. Selleck was under contract with "Magnum P.I." when he was cast to play Indiana Jones in "Raiders of the Lost Ark." Selleck was unable to get out of his contract in time to shoot the movie, so director Steven Spielberg went with Ford in his place.

Michael Corleone: Al Pacino became a household name after playing the son of a Mafia don who takes over the family business in "The Godfather." and its two sequels. The fact Pacino was cast at all was a minor miracle. Francis Ford Coppola met huge resistance from studio executives when he insisted on Pacino playing Corleone. He was a virtually unknown actor at the time and producers wanted a star in the role. Robert Redford and Ryan O' Neal were their initial choices and James Caan nearly had the part before executives relented after Coppola threatened to quit as director.

John Rambo: Sylvester Stallone emerged as an action star after his turn as the tormented Vietnam veteran in "First Blood." Stallone was only cast after the project sat in development hell for several years and the original choice for Rambo, Steve McQueen, died before production on the film finally got rolling.

Ben-Hur: No actor is more associated with Biblical and historical epics than Charlton Heston at the height of his film career. Heston won best actor for his most famous part: the title role in "Ben-Hur." At the time, Heston was an afterthought for the part. Burt Lancaster, Paul Newman, Rock Hudson and Leslie Nielsen all turned down the role before Heston accepted.

John McClane: Few actors have crossed from TV to movies with success equal to Bruce Willis. Two decades after "Die Hard" first debuted in theaters, Willis is still identified with the cop who is in the wrong place at the wrong time. He only landed the role after Arnold Schwarzenegger, Richard Gere and Sylvester Stallone all turned it down.

Marty McFly: Unlike many actors on this list, Michael J. Fox was the initial choice for the role that made him famous. Conflicts with his "Family Ties" shooting schedule nearly kept Fox out of "Back to the Future" and, for a time, he was replaced by Eric Stoltz. Fox returned to the role when Stoltz showed he wasn't right for the part of a time traveling hero with his uber-serious approach. Producers worked with Fox's TV schedule and the rest is history.

James Bond: Originating the role of Ian Fleming's suave and super-lethal British spy allowed Sean Connery to become famous for giving characters of all ethnic backgrounds a Scottish brogue. The world can thank Cary Grant for making that happen. Grant was offered the role before Connery, but he quickly rejected the offer because he did not want to be tied down to a film series.

Scarlett O'Hara: Bette Davis was the leading actress of the 1930s, but she turned down the lead role in "Gone with the Wind," the most popular film of that era, after a mistaken assumption on casting. Davis thought Errol Flynn was going to land the role of Rhett Butler and she did not like working with him. The part actually went to Clark Gable and Vivien Leigh was cast as Scarlett instead of Davis.