When Pixar's Monsters, Inc. premiered in 2001, it was an immediate box office success and further cemented Disney's partnership with Pixar Animation Studios. The premise of the movie was similar to Toy Story in that it highlighted a long-standing childhood belief: there are monsters living in bedroom closets. But Pixar didn't just leave it at that. The studio created a rich and full world in which their monsters lived. A world not unlike the human world in many ways but with a lot of quirky differences specific to its inhabitants.
Source：https://www.cbr.com/monsters-inc-monstropolis-origin/
