24. The Creature Effects Were Created Using Real Organic Material
Even 40 years on, there's something impressively and terrifyingly realistic about many of Alien's creature effects, especially in comparison to comparatively rubbery-looking props and creatures from films of the same era.
That's because the alien eggs, the facehugger and the chestburster were all made to look believable by using a variety of real organic materials.
The dead facehugger was made using shellfish and sheep kidneys, lots of animal guts were fired at the cast for the chestburster scene and the interior of the alien egg was made from cattle hearts and stomachs with a sheep's intestine for the facehugger tube.
Imagine how the set must have smelt under all those studio lights.