Hermione Granger’s half-Kneazle cat in J.K. Rowling’s Harry Potter books is Crookshanks. Hermione buys the large, ginger cat at Magical Menagerie in Harry Potter and the Prisoner of Azkaban.
Crookshanks is not an ordinary cat. The books explain that he is part Kneazle, a magical feline creature known for intelligence and the ability to recognize untrustworthy people. This helps explain why Crookshanks distrusts Ron’s rat, Scabbers.
Crookshanks appears to attack Scabbers, leading Ron to suspect that Hermione’s cat has killed him. The later revelation that Scabbers is actually Peter Pettigrew changes the meaning of Crookshanks’s behavior: the cat had recognized danger rather than randomly attacked an innocent pet.
Crookshanks is separate from Mrs. Norris, Argus Filch’s cat, and from the many other animal companions in the series. His unusual heritage makes him one of the clearest examples of magical creatures blending into everyday wizarding life.