The crystal at the heart of Shivers

leading from

Dreams That Become Films
and also
David Cronenberg  and Alien
(At the Alien Explorations Blog)

a) The Dream
David Cronenberg's film "Shivers" started with a dream in which two people were lying together in bed at night and the man wakes up, looks over to the woman and sees her mouth open and out of the mouth comes a spider and walks out of her mouth, goes around the house and goes back into her mouth, into her body.. It wasn't a horrific dream, it was just "Oh yeah. the spider that lives in her mouth" and it just lived there. During the day the woman herself would know nothing about it.

b) Reflection
He thought to himself in reflection, "My God, that image is really giving a physical presence to the idea that things go on within us which are strange and disturbing."Also, it seemed the spider in some way gave her life when she was awake.

c) Further development
Embodying that in an insect or creature was really the unique thing about the dream, but he couldn't actually do a spider because it's really hard to make a creature like that with legs that worked, so it became a slug like parasite. And that image was really the crystal around which the rest of the film Shivers formed.

Source quotes

1. David Cronenberg: Shivers did start with a dream I had about a spider that emerged from a woman's mouth at night while she slept. The dream was very casual. It wasn't a horrific dream at all. It was just , "Oh yeah, the spider that lives in her mouth." It seemed the creature just lived there, inside her. It would come out at night, go around the house and go back into her mouth. Back into her body. During the day she knew nothing about it. Afterwards, on reflection, I thought, "My God, that image is really giving a physical presence to the idea that things go on within us which are strange and disturbing. " Also, it seemed the spider in some way gave her life when she was awake. Embodying that in an insect or creature was really the unique thing about the dream. That was really the crystal at the centre of what became Shivers.  (Cronenberg on Cronenberg by Chris Rodley, original hard back edition p43, 1992) 
2. David Cronenberg: It was basically an image that I had, and I can't remember whether I dreamed it or read it somewhere but it was two people lying in a bed at night and the man wakes up, looks over to the woman and sees her mouth open and out of that mouth comes a spider and walks out of her mouth, and that image was really the crystal around which the rest of the film Shivers formed. I couldn't actually do a spider because it's really hard to make those legs move especially on a low budget, so it became a parasite. (Film Four interview, 2001  http://www.youtube.com/watch?v=BUdyX71jFYA)