The folks at Pixar are really messing with us this morning, releasing four different teaser trailers for 'Monsters University,' the prequel to their 2001 smash hit 'Monsters, Inc.' The movie is scheduled for a summer 2013 release.

As you will learn in each of the teasers, the premise of 'Monsters University' is that monsters aren't born scary. Instead Mike and Sully and the rest of the gruesome gang had to go to college to learn how to be the frightening closet dwellers they were in 'Monsters, Inc.' Check out three of the trailers below and head over to ScreenCrush for an exclusive fourth trailer.

Could you spot the subtle differences in the four trailers? If you could, you have graduated 'Monsters University' teaser watching university. Which we think means you are now fit to view the first full trailer for the film, whenever that comes out.

Are you excited for 'Monster University?'