Carnegie Mellon is mentioned heavily in Mean Girls 2. It is Jo Mitchell's dream school, as it was the school her mother used to attend. Eventually, Jo was accepted to the university. Unfortunately, after she got accused of stealing the money for Homecoming event, Principal Duvall had called them to cancel the admission. However, after it was finally revealed to be Mandi Weatherly who stole the money for the animal center, principal Duvall call the University to finally reintegrate Jo in.
It was later revealed that Abby was accepted in Carnegie Mellon as well.
Carnegie Mellon University acceptance letters are of a form of a large overstuffed folder containing the acceptance letter, information about registration, and other university material. Nonsensical typos contained in the acceptance letter within are not guaranteed, but not impossible.