Trivia: When the monsters are on the scare floor to start scaring, they scare for a while, then it shows a blue monster quickly running out of the door saying that the kid almost touched him. When you see the monster running out. look closely because you can see the same poster that Sid has in his room in Toy Story.
Trivia: Towards the end, just after Mike yells "I'm on the cover of a magazine.", he waves the magazine around (it's "Business Shriek"). On the back cover of the magazine, there is an ad for a monster-styled Macintosh computer. The layout of the ad resembles the layout of Apple ads; the Apple logo, and a slogan "Scare Different" that resembles Apple's "Think Different", are blurred but still recognizable, at the bottom of the ad. This is visible for less than a second, and is best seen by single-stepping the frames on the DVD. Why Macintosh: Steven Jobs is the CEO of both Apple Computer and of Pixar, the company that animated Monsters Inc. (01:23:16)
Trivia: When Sully goes into one of the rooms, I believe he is looking for Boo's room, there is a set of bunkbeds, and if you look, under the top bunk, is a poster for Monsters, Inc.
Trivia: After the Harryhausen's scene the voice of the CDA agent that says "building clear, proceed with contamination" is voiced by the director Peter Docter.
Trivia: Near the end of the film when Sullivan takes Boo back to her room and she is handing him her different toys, one of the toys she hands him is a Jessie doll. Jessie is the Cowgirl in Toy Story 2. If you look even closer you will notice that she also hands him the ball from "Luxo," one of Pixar's first animated shorts.