9. Meryl Streep - Ellen Ripley (Alien)
Despite the fact that Ellen Ripley, as played by Sigourney Weaver in four
Alien movies, has become one of the most defining characters in cinema history, you maybe surprised to find out that the role was firstly supposed to be embodied by a man, and secondly, Meryl Streep. Despite the fact that she's is one of the greatest actresses of all-time, though, I think that she would have been totally and utterly wrong for the part of Ripley. Why? Because, despite all the great performances that Streep has given over the course of her career, I'm just not buying her as an action hero. It just doesn't compute for me. And it hasn't computed for anybody else in the last thirty years or so either, apparently, given that Streep never did find herself poised as an action star. Thank God. Rumour has it that the role came down to either Streep or Weaver, but Ridley Scott eventually decided that Weaver was better suited. Yup.