A knight in one of the Hogwarts paintings. After Sirius Black attacks the Fat Lady, he takes over for her and guards the Gryffindor portrait hole. The Gryffindors don't like him as his passwords are complicated and change constantly. Dumbledore fires him after he lets Sirius Black into the Gryffindor common room with a list of passwords.
Sir Cadogan Character Timeline in Harry Potter and the Prisoner of Azkaban
The timeline below shows where the character Sir Cadogan appears in Harry Potter and the Prisoner of Azkaban. The colored dots and icons indicate which themes are associated with that appearance.
Over the next few days, the rumors about Sirius Black get wilder and wilder. Sir Cadogan replaces the Fat Lady, which annoys all the Gryffindors—he changes passwords all the time and... (full context)
...up with Hermione. When they get to the portrait hole, they find Neville pleading with Sir Cadogan . Apparently, Neville wrote down the passwords for the week and lost his list. Harry... (full context)
...Ron finally shouts that Sirius Black was in the dormitory and tells McGonagall to ask Sir Cadogan if he let Black in. Suspiciously, McGonagall steps out of the portrait hole and Sir... (full context)