(Monsters University) Sulley's dad, William Sullivan, was a famous Scarer and Sulley followed his father's footsteps and became a Scarer. Sully meets Mike at college and though they didn't get along at first, they end up being good friends. Sulley worked his way up to become the top Scarer.
(Monsters Inc.) Sulley meets a little human, girl. The Monster World is scared of humans because they are toxic, but they need their screams for power. Sulley works for a company that collects children's screams to power the city. Sulley's job is to get the kids to scream so they can collect them. Sulley, like his father, is the top Scarer in the company. Randall, another Scarer, wants to beat Sulley so he cheats. Randall gets screams after closing. Sulley sees one of the doors and looks inside, doing so he lets out the girl. He tries putting her back but Randall comes. Sulley finds Mike and they hide the girl. Sulley dresses her up as a monster and takes her to work. There they find that there are monsters everywhere in the company looking for the child. Randall finds out that Sulley and Mike have the kid and he tells them that he can get her back if they go to the scare floor during lunch. They go to the scare floor where they find her door. Sulley has grown to care and love the girl and called her Boo. When he sees the door he feels that something is off. Mike goes in the room to prove that it's safe but he was wrong. Randall was in there and he kidnapped Mike, thinking it was Boo. Sulley follows them to a room where he finds out that Randall has made a machine that sucks out screams. Sulley rescues Mike and they find the Manager of the company, Henry J. Waternoose III to tell him about Randall. Waternoose is with some new students and employees and he wants Sulley to demonstrate what a good Scarer does on the simulator. Sulley tries to get out of it but can't. He Roars and it scares Boo. Boo's costume then falls of revealing that she is the human. Waternoose banishes Mike and Sulley and decides to use Randall's invention. Sulley finds a new door to get back to the Monster World and save Boo. He and Mike are able to get Boo and they also get Waternoose to confess. Waternoose is arrested and Boo goes home but her door was shredded. Sulley would never see her again, or so he though. Mike was able to find every piece of the door and put it back together. Now the Monster World is powered by human laughter.
(Monsters Inc.) Sulley meets a little human, girl. The Monster World is scared of humans because they are toxic, but they need their screams for power. Sulley works for a company that collects children's screams to power the city. Sulley's job is to get the kids to scream so they can collect them. Sulley, like his father, is the top Scarer in the company. Randall, another Scarer, wants to beat Sulley so he cheats. Randall gets screams after closing. Sulley sees one of the doors and looks inside, doing so he lets out the girl. He tries putting her back but Randall comes. Sulley finds Mike and they hide the girl. Sulley dresses her up as a monster and takes her to work. There they find that there are monsters everywhere in the company looking for the child. Randall finds out that Sulley and Mike have the kid and he tells them that he can get her back if they go to the scare floor during lunch. They go to the scare floor where they find her door. Sulley has grown to care and love the girl and called her Boo. When he sees the door he feels that something is off. Mike goes in the room to prove that it's safe but he was wrong. Randall was in there and he kidnapped Mike, thinking it was Boo. Sulley follows them to a room where he finds out that Randall has made a machine that sucks out screams. Sulley rescues Mike and they find the Manager of the company, Henry J. Waternoose III to tell him about Randall. Waternoose is with some new students and employees and he wants Sulley to demonstrate what a good Scarer does on the simulator. Sulley tries to get out of it but can't. He Roars and it scares Boo. Boo's costume then falls of revealing that she is the human. Waternoose banishes Mike and Sulley and decides to use Randall's invention. Sulley finds a new door to get back to the Monster World and save Boo. He and Mike are able to get Boo and they also get Waternoose to confess. Waternoose is arrested and Boo goes home but her door was shredded. Sulley would never see her again, or so he though. Mike was able to find every piece of the door and put it back together. Now the Monster World is powered by human laughter.