Sigourney Weaver almost rejected her role in 'Alien'.

The 67-year-old actress has admitted she was hesitant about starring in the 1979 fantasy thriller, in which she portrays Ellen Ripley in the production, because she thought it was a ''very, very bleak script''.

Speaking about her first thoughts on the project to the Sydney Morning Herald, she said: ''It was a very, very bleak script.''

And the star was even more disappointed that she has graduated from Yale School of Drama to be cast in the franchise.

She added: ''I survived drama school to do this?''

But it wasn't until Weaver spoke with 79-year-old director Sir Ridley Scott that she had a change of heart, and realised the movie was going to be completely different to what she had initially thought.

She explained: ''It wasn't till I met Ridley Scott and saw these amazing drawings by [Alien concept artists] H.R. Giger and Carlo Rambaldi of the alien itself that I thought, 'Oh. Well. I've never seen anything like this.'''

The 'Alien' franchise has continued to expand, which has seen an additional five follow-ups released over the years, and Weaver thinks the success of the films are due to the actors projecting their own ideas on the supernatural figure, and because the movies have a ''malevolence that's beyond reality''.

Speaking about the film and its reception, the 'Avatar' star - who has 27-year-old daughter Charlotte with her husband Jim Simpson - said: 'I think each of us as actors loaded the alien with other meaning for ourselves. That's one of the reasons the film has traction - because it's not just this thing. It has this malevolence that's beyond reality.''