Doors are portal-like devices used by Monsters, Inc. and Fear Co. in the Monsters, Inc. franchise. Scarers use this technology to enter the Human World and scare children. The doors tend to match their target's design in terms of appearance. As most kids know, a closet door is one of the few things capable of keeping monsters at bay. With this simple dividing line, the Pixar team created worlds for both sides of the door. Each side had its own rules, the most important of which was…