In order for the filmmakers to make the main hallway of the underground facility connect to all the adjacent sets, they had a 10 foot by 8 foot false wall created. The wall was then transported to every set and placed outside the entrance to give the impression that every room connected with the main hallway.
On the set, the collars (made from plumbing snakes) would turn into spring loaded projectiles if they weren't put on properly. On one occasion, the lead actor's collar popped off and hit the director in the face.
Two different types of worms were used during the acid scene. The smaller ones were stuck to the actor's faces and the larger ones were held in their mouth till their lines were to be delivered.