Alien: Enter Veruschka

Leading from 

Looking for the Alien's Nucleus

Verushka

a) Searching for female forms
They started looking at women, and actually Giger claimed to have come up with the suggestion of using Vera Gräfin von Lehndorff-Steinort also known as the model Veruschka, someone who had changed ­fashion for good. She was the first super model of the 1960w. Her height was known to be 6 foot three and with its improbably long limbs, was revolutionary at the time, ­following an era of women with much fuller figures. The idea of associating danger and sexual desire, to have a creature that was at once desirable and lethal excited Ridley who was thinking about two women battling one another. It was the eroticism in Giger's work that had struck Ridley immediately, where everything is merged in his organic looking paintings. 

b) Enter Veruschka
Verushka herself came in, and so Ivor saw her there she was wearing a little pair of knickers and they always asked her to crouch down. Ridley thought about the form of a praying mantis, and how the knees would be impossibly high like a grasshopper. With great interest, Ivor found himself photographing her in various states of undress using the polaroid camera for the Alien. However

c) Giving up

The idea of two women battling one another as great as it would have been, Ridley realised there were practical problems, they couldn't find a woman tall enough for exactly what they wanted and by general agreement they had to give up the idea. The alien would be transformed into a man with a feminine shape, in essence a hermaphrodite.

Veruschka (source http://www.formidablemag.com/veruschka/)

Source quotes

1. Ridley Scott: Originally I wanted a very feminine creature, long limbed in the style of Verushka . The idea of associating danger and sexual desire, to have a creature that was at once desirable and lethal and that was exciting.  It was the eroticism in Giger's work that had struck me immediately. Everything is merged, it's a very "organic" painting. All the while there were practical problems and, by general agreement, we had to give up the original idea. The alien was transformed into a man with a feminine shape - a hermaphrodite. (Film Illustrated. v9. n99, Nov 1979, "Duelling with Death, The Alien World of Ridley Scott") 
2. Ivor Powell: The person that put the suit on had to be A, impossibly tall, we wanted them to be incredibly long limbed, especially from the waist to the knee, and erm, so we started looking at women, and I...and  it fell on my job to sort of er, you know, to try and bring in women on, I remember one of the tallest models, and quite a well known model of the time was this woman called Verushka, and she came in, and well literally, there she was, you know, in a little pair of knickers, erm and we always asked her like to crouch down, Ridley had this idea that it would be like a sort of praying mantis, and the way when you sort of crouch down, the knees sort of are impossible high, so, like a grass hopper, and so we went through all these pre-ambulations of trying to cast women so lucky Ivor, unfortunate Ivor had to photograph and take polaroids of all these women in various states of undress, you know, for the Alien," (Alien Makers II documentary) 
3. Ridley Scott: When I started Alien I wanted to not only have a strong heroine, but I also wanted to make the creature female as well: two women battling one another would have had a great sexual connotation. (David Lewin, Daily Mail,1/10/79) 
4. Ridley Scott: I wanted the alien in human form very sensual and take on a female shape. I had to abandon the idea because we couldn't find a female tall enough. (David Lewin, Daily Mail,1/10/79)