Ellen Ripley - Alien (1979)
The original choice: During the early auditions, casting director Mary Goldberg lined up two women for the New York sessions. One had a few credits to her name and is now the most beloved actress of a generation - Meryl Streep. Due to a personal tragedy, the multiple Oscar-winner didnt audition but that second name, a young theatrical upstart, went on to snag it...
Who they went with: Sigourney Weaver, who was reluctant to make her cinematic debut in a sci-fi movie. However Ridley Scott convinced her after she witnessed some of monster designer H.R. Gigers concept art.
Superman - Superman (1978)
The original choice: This would have made for a Superman as damnedly intriguing as Nic Cages. Heading up early shortlists was an up-and-coming actor who would go to deliver some of cinemas most compelling vocal performances -- Christopher Walken.
Who they went with: Director Richard Donner and his team of producers eventually decided to cast an unknown face in the role of Clark Kent, and that lucky actor was Christopher Reeve.
Bruce Wayne - Batman (1989)
The original choice: Appearing on several early shortlists for the part of billionaire crime fighter Bruce Wayne, Michael J. Fox duked it out with a ton of other A-listers for the titular role. He was also the studios favourite to play Batmans sidekick Robin which director Tim Burton held off on casting for a few years.
Who they went with: The man who would later play homage to the role in Birdman -- Michael Keaton.
Neo - The Matrix (1999)
The original choice: Two huge A-listers were up for the part of Thomas Neo Anderson in The Wachowskis seminal sci-fi epic The Matrix; Tom Cruise and Will Smith. The latter of which has gone on the record as stating his relief at not botching up the part.
Who they went with: After a period out of the spotlight Keanu Reeves invigorated his career with his spot-on approach to humanitys saviour.
Rick Deckard - Blade Runner (1982)
The original choice: Ridley Scott and producer Michael Deeley worked together with Dustin Hoffman to craft a darker, more embittered version of the cult character. Despite his enthusiasm for the part, his desire to tone down Deckards involvement in action-heavy scenes led to his departure.
Who they went with: Hot off Star Wars, Harrison Ford stepped in as the leading man Scott and Deeley were after and nailed the part as written.
O.J. Simpson - The Terminator (1984)
The original choice: Dubbed too nice by producers who believed his affable persona would make it impossible for audiences to believe he was a killing machine, O.J. Simpson was the first choice to play The Terminator.
Who they went with: An actor-politician who is now synonymous with the role, Arnold Schwarzenegger. The T-800 would go on to become his signature performance that hes set to revive again for the fourth time in this summers Terminator: Genisys.