
Wikipedia
In the parallel universe of monsters, Mike is not scary but still dreams of
becoming a scarer (those who make the children scared to harvest their scare
energy). As he grows up, Mike joins Monster University and enters the scare
program. He also meets Sulley, an obviously scaring monster, son of a famous
scarer, who unlike Mike does not take his studies seriously, but instead
relies on his inherited talent. Despite having studied hard and because of
his rivalry with Sulley leading to the destruction of the dean's trophy for
extreme scariness, they both fail their end-of-term exam and are expelled from
the scare program. Mike then enters the Scare Games, betting with the dean
that if he win the games he can continue studying to become a scarer (and
would leave the university otherwise). As he needs a team, he is adopted by
OK, the least popular fraternity on campus, and convinces Sulley to join them.
Mike coaches the team and they are more or less ready to enter the
competition. They manage to not get eliminated until the last round of the
games where they compete against the team from the popular ROR fraternity.
Mike's team wins the scare simulator tests thanks to Mike's exceptional score,
but he soon discovers that Sulley had tampered with the simulator to make sure
they would win, putting doubt on his ability to scare a child. To prove
himself, he enters the world of humans through an experimental door developed
at the university, and fails to scare a sleeping child. He soon discovers that
he is in the dormitories of a summer camp; in the meanwhile, Sulley follows
Mike to take him back, and is mistaken for a bear by the humans. At the same
time, the door is powered down by university's authorities, preventing the two
monsters from coming back. But Mike reasons that with enough human scare
energy, it would be possible to power the door. He orchestrate a scary
situation for Sulley scare the humans as much as possible, generating more
power than has ever been generated. Despite their feat, Mike and Sulley are
expelled from the university, but enter Monster Inc. as mailmen, and quickly
go up the ladder and eventually both of them become scarers.