In among various more innocuous things: he defeated a basilisk, which nobody in the school had thought was there until he told them and which just happened to come straight to his location shortly thereafter. Said basilisk was accused of petrifying people, which there is no record of basilisks ever doing. He hasn't denied rumors of his nonhuman ancestry, and no information could be obtained about his parents or other relatives. He can fly with his wings, which would require an extremely complicated and frequently-maintained transfiguration for a wizard to accomplish, but has shown no signs of transfiguration prowess and claims to be doing a different kind of magic. Every current professor he has interacted with was seen looking unusually tired afterwards, and none of them have questioned his desire to stay at a school full of children despite not being either an employee or a student.
Meanwhile at Hogwarts, Ginny Weasley is hiding in her dorm room, a sixth-year Hufflepuff and all his possessions have been turned lime green, and Fred and George have detention.