25 Things You Didn't Know About Alien
19. Sigourney Weaver Was Almost Recast Because Of A Possible Cat Allergy
On the first day that Sigourney Weaver shot a scene alongside Jones the cat, she began reacting extremely badly, her skin itching and breaking out in a rash - leading her to fear that she may be allergic to cats.
As Jones was actually played by 4 different but identical-looking cats, each of which fulfilled different "dramatic" roles, the crew felt it would be easier to recast Ripley than to find another 4 identical cats.
Luckily, it transpired that Weaver was not allergic to cats at all, and the reaction was to glycerin sprayed on her skin to simulate sweat.