Players can choose to train as either Sully or Mike (switching easily between the two at any point in the game), with each character having distinct scare tactics appropriate to their personality - Sully's scares are ferocious and intense, while Mike's are a little more comical. Each Monster also has his own special moves - Sully is the master of the Tailspin Slap Attack, the Monster Fur Flop Aerial Pounce and the Somersault Jump, while Mike spreads terror with the help of the Spinning Ball Attack, the Bouncing Eyeball Aerial Pounce and the Double Hover Jump.
Sully and Mike are helped along the way by a team of professional 'Scare Trainers', including the speed trainer Randall (who must be beaten in special challenges to unlock some of the game's levels), orientation trainer Roz and Mr. Waternoose - the big boss at Monsters, Inc. and acting Dean of Scare Island.
The action takes place on Terror Isle, which incorporates three main training grounds - Urban, Desert and Arctic - with each ground housing new scare targets appropriate to their setting. As children are so dangerous to the Monster world, Scare Island's scare targets come in the form of 'Nerves', a docile branch of the Monster family tree which exists solely to train Scarers. When a Nerve is successfully terrorised, a scream canister is filled and the Nerve is temporarily turned white.
As Mike and Sully progress through their training, they are rewarded with 'Certificates of Terror Accomplishment'. Then, when the two monsters have finally graduated (and are accepted as fully-fledged employees of Monsters, Inc.) they are offered the opportunity to go through the whole island once again - but this time as 'Top Scarers'!