John Carpenter was not the original target for director. An initial attempt was made to engage the services of Tobe Hooper. Hooper wrote a script for the film in four weeks. It was not taken up by Universal and the project finally landed with Carpenter.
The jelly that the thing squirted out was KY Jelly. The dog thing was an animatronic hand puppet, because they wanted the movement to be more organic. Norris's head was a hydraulic rod that pushed the head off and the goo was melted rubber and gum. None of the things were people in suits and they used remote controls to move most of them. At the end, where the thing is moving under the boards, it was actually a steel ball being pulled by a winch.