- "I need scarers who are confident, tenacious, tough, intimidating. I need scarers like... like... James P. Sullivan."
- —Henry J. Waternoose III
- "You're the boss. You're the big hairy boss."
- —Mike, as Sulley enters through the first door of the day
In the first film, Sulley was top scarer of Monsters, Inc., and was naturally afraid of humans, due to their rumored "toxic touch" that could kill the biggest monsters in an instant... until he met Boo, a human girl who found her way into the monster world and into the factory. Sulley, who was initially hesitant, became Boo's protector and obtained a fatherly role to the human. Constantly worrying about her and protecting her from harm while at the same time unlocking the secrets that humans were not as deadly as rumored. Starting by treating Boo like a pet, he eventually grew to care for her, the attention drawing away from a jealous Mike. Randall Boggs, Sully's rival who also wants to be top scarer, tries to use Boo in an experiment to forcibly extract screams for the growing energy crisis that relies on their cries to provide, and risking his friendship with Mike, Sulley comes to her rescue and in the process discovers that a child's laughter is 10 times more powerful than scream. Sometime after Mr. Waternoose, the CEO of Monsters, Inc., is arrested by the CDA, Sulley becomes the new CEO and changes the policy to obtain children's laughter instead, apparently turning the energy crisis around.
Sometime after the events of the film, Sulley announces Put That Thing Back Where It Came From Or So Help Me, a company play that stars Mike, who has also directed, written, and produced the play, in front of the audience, and he appears in the play as a co-star.
Mike's New Car
In the short, Sulley is featured as the secondary protagonist. When he sees Mike's new car, he asks Mike what was wrong with the old car, to which Mike replied, "That's three little words, Sulley: Six-wheel drive!", then they both got in. Unfortunately for Mike, Sulley accidentally ruins the car by doing various different things, and Mike eventually told Sulley to get out, but ruined the car himself when he sped off.
Sulley is set to reappear in the prequel. He will look shorter, skinnier and shaggier.
In the first film, although his job is to scare children, Sulley makes efforts to befriend Boo, and then goes to extreme measures to protect her from Randall. It is Sulley who realizes that making children laugh is a far better way to produce energy than making them scream, thus solving Monstropolis' energy crisis.
Sulley is also very loyal to Mike, going so far as to lend him "odorant" and making reservations for him at an exclusive restaurant on Mike's girlfriend's, Celia, birthday. Sulley also attempts to cover for Mike when Mike realizes that he has forgotten to turn in his paperwork. In return, he relies on Mike to help him in his madcap efforts to keep Boo safe from Randall. When Mike protests, Sulley chooses to help Boo over appeasing Mike's pride; his choice is justified when Mike later changes his mind and comes to help him and Boo.
- Sulley appears in the end credits of Cars as a giant monster truck. He is also seen in Tokyo Mater with a car version of Mike.
- Sulley was originally going to be a janitor and not a scarer in one early version.
- According to the original treatment from the DVD, Sulley's working name was Johnson and instead of being the best scarer as seen in the movie, he was a clumsy monster who was very bad at his job.