Sigourney Weaver's odd audition

Sigourney Weaver acted like a possessed dog during her audition for Dana Barrett - and it inspired the climax of the film.

Late director Ivan Reitman told the ReelBlend Podcast: "She shows up, and she says, 'You know, there's a mistake in your script. And I said, 'What's that?' And she said, 'Well, I should be possessed. I should be like a dog. And I can act like a dog.' And then she literally climbed on my low coffee table and, you know, went on her hands and knees and took on this position. She started howling! Okay, this woman is definitely the part. And she has a great idea."