"At first I was hired just to do designs. Ridley Scott told me, ‘You make the designs and we’ll find someone who can build them exactly the same.’ I liked this because I could stay in Switzerland and just fly to London once in a while to show them my work. So I began to work on Alien day and night because the time to do it was very short and I had no experience in working on a film like that. I wondered if it was possible for someone else to transform my stuff in three dimensions; but there are a lot of specialists around, so I was very hopeful.”
Giger then spent the next year working on the movie, performing design and production duties far beyond his original remit, including spray painting the spacewreck set to meet his color choices, reconfiguring the alien (based partially on his painting Necronom IV) to work better on screen, and even touching up the xenomorph’s paint job every day after filming.
(Quote and images from Cinefex #1.)