* A massive, furry, blue, and purple monster with two horns and large blue fur.
* He is the top scarer at Monsters, Inc. and best friends with Mike Wazowski.
* Sulley is a kind-hearted and caring individual who is fiercely protective of his friends and family but can be clumsy at times.
Michael "Mike" Wazowski
* A small, green, one-eyed monster with no fur and sharp teeth.
* He is Sulley's best friend and works as his scare assistant at Monsters, Inc.
* Mike is a witty, intelligent, and resourceful monster who is always looking out for Sulley's best interests.
Randall Boggs
* A mischievous, cunning, and ruthless monster with purple fur, long arms, and legs, and a chameleon-like tail.
* He is a scarer at Monsters, Inc. and is in competition with Sulley and Mike for the top spot.
* Randall is willing to do whatever it takes to get ahead and is not afraid to use underhanded tactics to achieve his goals.
Henry J. Waternoose
* The CEO of Monsters, Inc. and the main antagonist of the film.
* A large, overweight monster with gray fur, a bulbous head, and a handlebar mustache.
* Waternoose is a greedy and power-hungry individual who is willing to put the lives of his employees at risk to achieve his goals.
Roz
* A no-nonsense, tough, and efficient monster employed as a secretary and the CDA agent.
* She is dedicated to her job and is always on the lookout for any suspicious activity at Monsters, Inc.
* Roz is known for her sharp tongue and her ability to get to the bottom of any situation.
Celia Mae
* A large, cyclops-like monster with pink fur, one big eye, and a kind and caring personality.
* She is Mike Wazowski's girlfriend and is always supportive and understanding.
* Celia is a loyal friend and is always there for Mike when he needs her.
Boo
* A human toddler who accidentally enters the monster world and becomes Sulley's friend.
* She is a curious and adventurous little girl who is not afraid to explore new things.
* Boo brings joy and laughter to the monsters' lives and helps to teach them about the importance of friendship and family.