Mike's parents were originally planned to be included in the story. They would drop Mike off for his first day at Monsters University. However, director Dan Scanlon decided to drop them from the finished film to make Mike seem just that much more vulnerable.
Professor Knight's lecture hall is room A113, a reference to a room at CalArts where animation classes are taught. All Pixar films have a reference to "A113".
The Pizza Planet truck, first featured in Toy Story can be seen parked by the left of the ROR sorority house during the party. This truck is present in all Pixar feature film so far.
When Mike is riding the pig through a fraternity house, one can spot a poster of the 1976 KISS album "Rock And Roll Over" on the wall in the right corner.