A ferret is a small, carnivorous mammal. While they exist as regular animals in the wizarding world, their most notable appearance in the series is the result of a Transfiguration spell. In 1994, after a lesson on the Unforgivable Curses, Draco Malfoy attempted to attack Harry Potter from behind in the Entrance Hall of Hogwarts. The new Defence Against the Dark Arts professor, Alastor Moody (secretly Barty Crouch Jr. in disguise), witnessed the act and swiftly transfigured Malfoy into a ferret as punishment. The ferret was described as being sleek, white, and pointed, mirroring Malfoy's own physical characteristics, particularly his pale blond hair. Professor Moody then magically bounced the terrified ferret up and down on the stone floor, a spectacle that Ron Weasley found immensely amusing. To further humiliate him, Moody levitated the ferret over to Gregory Goyle and dropped it down the front of his robes. Minerva McGonagall arrived and, appalled at the use of Transfiguration as a punishment, reversed the spell, returning a furious and humiliated Malfoy to his human form. The incident became legendary among Hogwarts students, and Malfoy was taunted with the nickname “the amazing bouncing ferret” for years afterward, particularly by Ron Weasley. Ferrets are also mentioned as ordinary animals within the wizarding community. During Harry's visit to the Magical Menagerie in Diagon Alley in 1993, he overheard a witch complaining that she was having her ferret “re-boned,” indicating they are kept as pets or companions and are subject to magical remedies.
The transfiguration of Draco Malfoy serves several key purposes in the narrative: