Crookshanks

Crookshanks is Hermione Granger's pet cat. Crookshanks is part Kneazle and is very intelligent.

In Harry Potter and the Prisoner of Azkaban, Crookshanks played an instrumental part in Sirius Black's attempts to enter Hogwarts Castle and lay hands on Peter Pettigrew, who was masquerading as Ron Weasley's pet rat, Scabbers. Crookshanks met Sirius (who was in Animagus form) out on the grounds several times; he also stole the passwords, which Neville Longbottom had written down, into Gryffindor Tower and gave them to Sirius. Despite all Crookshanks' help, Sirius was still unable to catch Scabbers inside the castle, and resorted to kidnapping Ron outside one evening. Despite everything, Pettigrew still escaped.