Dawson Casting: According the official website, Terry and Terri are juniors, placing their age at about twenty years. At the time the film came out, Terri's voice actor was 43 and Terry's voice actor was 50. Indeed, in most languages, the students are not voiced by college-age actors.
Disney Press also produced a Monsters University Yearbook (meant to be Mike's and signed by numerous characters) as a tie-in, though done in a more illustrated style resembling concept art and the opening titles.
Deleted Role: Waternoose (recast as Kelsey Grammer) almost made an appearance, but Grammer's cameo was cut from the film. Waternoose appears only in a photograph.
The Italian dub did not use any of the "Monsters Inc." voices except for the Yeti's. Partially due to the fact that Tonino Accolla (Mike) died before the film got dubbed.
European French: Sulley and Randall were recast because neither Jacques Frantz (Sulley) or Dominique Collignon (Randall) could voice a younger charcater. They were respectively recast with Xavier Fagnon and Jeremy Prevost.
Swedish dub: While Sulley, Randall and Roz have the same voice actors as in Monsters, Inc., Mike and the Yeti were replaced. Interestingly, Mike had his original voice in the trailer.
Brazilian dub: In the first movie, Roz was voiced by Brazilian singer Gottsha (who also done voice work on the brazilian dub of Tangled as Mother Gothel). For her small cameo in Monsters University, her voice was provided by Manolo Rey (who's know for doing the voice of Tobey Maguire in the brazilian dub of Sam Raimi's Spider-Man Trilogy)
Arabic dub got it Up to 11 due to the fact that thanks to the then-current Disney politics instead of being dubbed in Egyptian Arabic (like the previous movie), Monsters University (as well as all new Pixar films and redubs of older ones into MSA for Jeem TV airings since early 2013) was dubbed in Lebanon in MSA instead.
Barbara Ratthey, the original German voice of Roz, had died a few years prior so instead she was voiced by Luise Lunlow. Martin Semmelrogge, who voiced Randall i the original film, could not voice the younger Randall, so Tim Sander replaced him.
According to Dan Scanlon, the movie originally opened with Mike's parents dropping him off at the university on his first day there, and Billy Crystal actually voiced his whole family! It was cut from the film due to Scanlon wanting to remove parental guidance from Mike's college life.
Other early drafts included Mike and Sulley in grade school together (to respect the "fourth grade" quote in Monsters Inc.) It reached storyboards process. Then Pete Doctor advised Scanlon to disregard the quote to stick to the focus of the University.
Characters of Celia, Fungus and Waternoose (recast as Kelsey Grammer) originally were to make appearances. Grammer's cameo was cut from the film; Waternoose appears only in a photograph.
Not surprisingly, the filmmakers tried to make it Sulley's story until they saw the story potential in Mike's struggles. Some concepts they experimented with was that Sulley initially wanted to be a dentist and suffered a case of Disappeared Dad. These scenes would have probably explored Sulley's relationship with the unseen Bill Sullivan.
Originally, Monsters University was going to be a sequel to Monsters Inc. and was called Monsters, Inc. 2: Lost in Scaradise, which was created by Circle 7. It would've been about Mike & Sulley dropping by Boo's room to wish her a happy birthday, only to discover that somebody different is sleeping in Boo's room. It seems that Boo and her family have moved since Mike and Sulley last visited her. Sulley is so determined to see Boo again that he and Mike venture out in the human world in order to find her. Once Mike and Sulley cross over into the human world, they then aren't allowed to return to Monstropolis until they actually reunite with Boo. It would also include an older Boo trying to hide Mike and Sulley from other people.
The "Art of Monsters University" book indicated there was a Bar Fight sequence involving an altercation between Mike and Johnny and the ensuring fight that did not make it in.
Claire Wheeler was originally designed as an Eta Hiss Hiss girl until the animators thought it would be fun to place a goth character on the top of the Greek Life council. Even earlier drafts had her as a bubbly drama student.
The Oozmas were originally humiliated at a Movie Night.
Hardscrabble was originally supposed to be male and yelled alot until Scanlon decided to feature a great female Scarer that was more sophisticated and intimidating.
Old designs of Mike had him wear braces until Scanlon realized he would have to avoid the argument that "Mike would be scarier without braces" so Mike was redesigned with a retainer he could remove.
One ending they experimented with was after Mike's and Sulley's expulsion, Waternoose drives up in a limo, hearing about Mike's and Sulley's brief stint in the Human World and offers them jobs. The idea was unsurprisingly rejected as it would negate the whole theme of hard work.
Don Carlton originally had fire-breathing abilities which he kept under control with pills. Eventually he would abandon the pills to make use of his fire-breathing.
Earlier storyboards seem to indicate that Terri enjoyed experimenting with personas, including becoming a goth, much to Terry's annoyance.