The Rogue Bludger

During the first Quidditch match of the season, a rogue Bludger relentlessly attacks Harry, seemingly possessed. Fred and George Weasley try to protect him, but the Bludger is clearly enchanted to target only Harry. Despite the danger, Harry manages to catch the Golden Snitch with one hand, winning the match for Gryffindor, but his arm is broken in the process. Gilderoy Lockhart attempts to heal the arm but instead removes all the bones, leaving it limp and rubbery. Harry is taken to the hospital wing, where he must regrow his bones overnight. The incident is later revealed to be Dobby's attempt to get Harry sent home, as the house-elf had enchanted the Bludger to protect him from the dangers at Hogwarts.