Really fun!
First prequel that Pixar has done.
Great music by Randy Newman.
OH MY GOODNESS NATHAN FILLION!!!!! I knew Johnny Worthington sounded familiar, but I couldn’t really place it. Although the same thing happened with all of the voices (except for the big three who came back from the first movie), which is weird (for me anyways).
Great tie-in to the existing universe (although one of my cousins pointed out that a line from the first movie presents a problem – spoiler below).
Spoiler Alert! (place and hold your mouse over the bar to see)
In Monsters, Inc., when Mike and Sulley walked through Monstropolis to go to the company, Mike said to Sulley “You’ve been jealous of my good looks since the fourth grade”. In this film, we’re told Mike and Sulley met in college. [In the commentary, director Dan Scanlon explained that there was a lengthy scene that would have followed Mike and Sully throughout their years in elementary school, but it would have slowed the pace of the film and would have reduced the impact of their rivalry. Rather than spend a lot of time on a back story, Scanlon decided to have Mike and Sully meet in college, even though this was inaccurate.]
Source: Deliberate mistake from film entry on MovieMistakes.com