J.K. Rowling revealed that Rita Skeeter was an Animagus who could become a beetle.
Rita Skeeter is a gossip journalist who appears prominently in Harry Potter and the Goblet of Fire. She writes sensational stories about Harry and other characters, often presenting speculation or private information as scandalous news. Her reporting creates pressure around the Triwizard Tournament and the return of Lord Voldemort.
The beetle form explains how Skeeter gathers information without being noticed. Hermione Granger eventually discovers the insect and identifies it as an unregistered Animagus. Hermione then forces Skeeter to stop writing harmful stories by threatening to report her illegal transformation to the authorities.
An Animagus is a witch or wizard who can deliberately transform into a particular animal. This differs from ordinary magical shapeshifting and from a werewolf transformation, which is involuntary. Rita Skeeter’s beetle form is therefore a key plot device and a notable example of hidden magical surveillance in the series.