Harry Potter and the Prisoner of Azkaban attacked by a big black dog, which Harry has seen several times before. The dog drags Ron through a tunnel under the Whomping Willow into the Shrieking Shack. Harry and Hermione follow, and there is a brief standoff when they find Ron with Sirius Black, who has transformed from the dog. Lupin enters, and they explain the situation to Harry and his friends: Lupin is a werewolf, which led to his friends James Potter, Sirius Black, and Peter Pettigrew becoming animagi. Lupin explains that Scabbers is Pettigrew in his animal form; he has been hiding from Black, whom he had
Fictional universe of Harry Potter mirror in "Harry Potter and the Order of the Phoenix", with a note explaining to Harry that Sirius and James Potter used to use the mirrors to talk to each other when they were put in separate detentions. In "Harry Potter and the Deathly Hallows", Harry uses a shard of his broken mirror to call for help from the Malfoy's cellar, and later finds out that Aberforth Dumbledore had been watching over Harry using Sirius' mirror, which he obtained from Mundungus Fletcher. Flying paper aeroplanes, (referred to as "interdepartmental memos") are used within the Ministry of Magic. In "Harry Potter