2. Mike & Sulley Meet In The Fourth Grade - Monsters University
When Pixar announced that they were going to make a prequel to Monsters Inc. focusing on heroes Mike and Sulley and their time at University, everyone went crazy thanks to a throwaway line in the original film in which Mike suggests that the pair have, in fact, known one another since the fourth grade, and didn't meet in college: "You've been jealous of my looks since the fourth grade, pal." If only Pixar would have known at the time that such a minor, seemingly generic line would cause them so much trouble when they decided to make a sequel a decade later, huh? Still, although Pixar don't bother to address this line in the final cut of Monsters University (we have to presume that Mike was just throwing out that line in jest in the first movie), they did originally set out to acknowledge the fact the pair knew each other as children. A deleted scene then, drawn but never animated, depicts the moment that they first met, with Mike trying to teach Sulley how to be scary. Eventually Sully ends up embarrassing himself, and Mike pokes fun. After a while, the team at Pixar realised they were going to too much effort, and scrapped it.
Should It Have Stayed In The Movie? It's interesting to note that this one scene would have re-established the entire Monsters Inc. mythology - merely cutting it out changes a hell of a lot. Still, shoe-horning in an unnecessary scene like this - despite the line in the first movie - seems like overkill, and Pixar were right to let it go. Who really cares, anyway?