The actor - who voices the one-eyed Mike Wazowski in the sequel - has discussed the closely-guarded Disney/Pixar project.
"[Mike and Sully] end up in the same fraternity where they have this scare competition - like Greek Games in college," Crystal told Entertainment Weekly.
"They have to mobilise a group, sort of like Revenge of the Nerds monsters, and get them ready to be scary."
He also revealed that the characters are "17 and 18 years old in the script".
"My guy has a retainer, even," he added.
The prequel sees the stars of the first film learning how to properly scare children at college, with John Goodman also returning as the voice of Sully.
Watch the Monsters University teaser trailer below: