Monsters Inc. Timeline
Monsters, Inc was only Pixar’s third animated movie, but was such a hit it warranted two sequels. In one of them, Monsters University, the creators managed to cause a bit of a continuity error.
Because in the original 2001 movie, we learn that Mike and Sully have been friends for a long time, at least since 4th grade.
But in Monsters University from 2013, we learn the two didn’t meet until college. Considering over a decade had passed between the two movies, maybe it’s not so surprising some mistakes like this one crept in.