Monster Inc. is the largest scream-processing factory in the monster world and James P. Sullivan (John Goodman) is their ace scarer. Nicknamed Sulley, he's huge, covered in blue fur, has big purple spots and horns. With his best friend and co-worker Mike Wazowski (Billy Crystal), a green, opinionated one-eyed monster, they try to frighten children. But frightening children isn't as easy as it used to be, what with scary computer games and television, the children are becoming harder and harder to scare and the monsters are facing a severe power crisis. Then Sulley commits the ultimate monster disaster - he accidentally lets Boo, a little girl, into monster world and pandemonium ensues. Sulley and Mike must quickly get Boo back to her own world, but they have a small problem - they can't find the door through which she came!