A skeletal and devious old cat that belongs to the cantankerous caretaker Argus Filch in J.K. Rowling's Harry Potter books, Mrs. Norris prowls the hallways of Hogwarts, trying to catch any students she can get in trouble. If she spots anyone breaking rules, she'll cause a ruckus to bring Filch to the scene of the crime so that they can be punished.

In the second Harry Potter book, Harry Potter and the Chamber of Secrets, Mrs. Norris was petrified (actually frozen solid) by the creature that was terrorizing the school. She was later revived, but it was a terrible experience for the entire school, coming in a series of such frightening incidents, which were finally resolved in the final chapters of the book.