Sir Cadogan in Harry Potter and the Prisoner of Azkaban

Sir Cadogan

Sir Cadogan is the rather demented portrait of a hapless knight who takes over as the guardian of Gryffindor Tower after the Fat Lady gets slashed up by Sirius Black. Sir Cadogan is eventually fired after letting Sirius Black in himself (whoops), and we assume he went back to starring in Monty Python specials, or something.