James P. Sullivan (John Goodman),

AKA Sulley, Covered in blue fur with purple spots stands 8 feet tall (not including horns). His impressive build and natural ability to scare have made him the Top Scarer at Moncters, Inc. Off duty, he’s the nicest monster around a down to earth guy with a good sense of humor. This combination has earned him the respect and admiration of everyone he knows, including the company’s CEO. 

Mike Wazowski (Billy Crystal)

Is a feisty and quick-witted, one-eyed green ball of a monster. His best friend and roommate is Sulley, whom he also assists at Monsters,.Inc. No one loves the profession of scaring more than Mike, and he is tremendously proud of Sulley’s highly esteemed scaring record. He's also pretty fond of the perks that come along with working for the top Kid Scarer.

Boo (Mary Gibbs)

The name given to her by Sulley – is an adorable, vivacious little girl who takes her journey through her closet door into the monster world in stride. Undaunted by the odd landscape, Boo takes an immediate liking to her new friends Sulley and Mike. Throughout her experience, Boo remains blissfully unaware of the potential danger she is in. She is having way to much fun!

Henry J, Waternoose (James Coburn)

A large crab-like monster with multiple eyes, Henry J, Waternoose, CEO of Monsters Inc., is the third generation of Waternooses to run the company. This grandfatherly monster is dedicated to the company today as he was when he first started as a Kid Scarer nearly fifty years ago.

Randall Boggs (Steve Buscemi)A calculating, lizard-shaped monster with eight arms, eight legs and a mouthful of sharp teeth, Randall has the chameleon-like ability to blend into his surroundings. This talent has made him the second best Kid Scarer at Monsters, Inc. But second best isn't good enough for the ruthlessly ambitious Mr. Randall Boggs. He’ll do whatever it takes to knock Sulley out of the number one spot.

Roz (Bob Peterson III)

Slow moving, slow talking, but oddly quick-witted, Rox is a slug-like monster who works as the Dispatch Manager at Monsters, Inc. Roz lives for paperwork, and if there’s one thing she can’t stand, it is an improperly filed scare report. Mike is a repeat offender, so Roz keeps a watchful eye on him.

Celia (Jennifer Tilly)

Is the receptionist at Monsters Inc. Though she does have live snakes for hair, she is anything but a Medusa. Celia is sweet beguiling, particularly to Mike. Things between Mike and Celia are getting pretty serious.