In the Harry Potter books, the inhabitants of the pictures on the walls of Hogwarts are alive, and can move to other portraits to visit each other.

The portraits in the Headmaster's office depict all former Headmasters of Hogwarts, who at times act to advise the Headmaster and are sworn to aid him in his duties. Notable among them is the portrait of Phineas Nigellus.

Other portraits include the following. It is not yet known whether these characters ever had a flesh-and-blood existence or not.

The Fat Lady

The Fat Lady is the guardian of Gryffindor Tower. She is often upset after being woken up. Years ago, the Fat Lady gave Molly Prewett and her future husband Arthur Weasley a real telling off when they were out of bed after dark. In Harry Potter and the Philosopher's Stone, she left to visit another portrait in the middle of night, locking up Harry, Ron, Hermione and Neville out of Gryffindor Tower. In Harry Potter and the Prisoner of Azkaban, the Fat Lady was attacked by Sirius Black and it was awhile before she dared to guard Gryffindor Tower again.

In the first movie (Harry Potter and the Philosopher's Stone) the Fat Lady was played by Elizabeth Spriggs . She did not appear in the second movie. In the third movie (Harry Potter and the Prisoner of Azkaban) she was played by Dawn French.

Sir Cadogan

Sir Cadogan is an eccentric knight who guarded Gryffindor Tower during Harry Potter and the Prisoner of Azkaban when the Fat Lady was recovering from her encounter with Sirius Black. Sir Cadogan was universally hated as he spent half his time challenging people to duel and the rest coming up with complicated passwords he changed frequently. He wasn't fired until after he let Sirius Black in when Sirius read the whole week's passwords off a list (compiled by Neville Longbottom who was unable to keep track of the changes). Sir Cadogan's portrait was already well-known at Hogwarts in Bill Weasley's day.

Sir Cadogan was played in the Harry Potter and the Prisoner of Azkaban movie by Paul Whitehouse.