Mike storms out of his dorm room to find a party going on in the hallway

Given the disco soundtrack and the fact that his classmates start dancing around Mike once he storms out of his room, its safe to assume to trailer is probably set in the Seventies.
He is unaware of his new body art, fuming: 'If you're going to prank someone, at least you can do is think of something clever.'
Voicing the trailer, Crystal had so many ideas, producers decided to release four slightly different trailers.

Not impressed: Mike storms out of his dorm room to find a party going on in the hallway

In one promo, the sleep-talking monster says: 'I can't go to class, I'm not wearing any clothes,' while in another he mutters: 'My homework ate my dog.'
In the third he says: 'My pony made the dean's list,' while in the fourth he mumbles: 'Class president? Ha ha ha.'
Director Dan Scanlon said: 'Billy Crystal's an amazing comedic actor.