Doors are a major way of going from room to room in the Monsters, Inc. factory from the movie Monsters, Inc. Scarers use this technology to enter the Human world and scare children. The main plot of the movie is about Mike and Sulley trying to return Boo to her door (shown to the right). In Monsters University, due to it being a prequel, all of the doors were much larger and clunkier in appearance, probably so that they all appear very old and outdated.