Why Harry Turned Into A Dragon
Since it's clear the author doesn't intend to give us an answer, it's up to us to devise one.
- The aliens at the epilogue did it somehow. Maybe some magic they did long ago that eventually landed on Earth and struck Harry.
- An Alternate Universe version of some canon character is responsible.
- Someone went back in time (but not with the Time Turner) to turn Harry into a dragon and make sure these events happen.
- A Wizard Did It
- Harry is a Were Dragon from his father's side. He's just never figured out the turning back to human part.
- It was his magic reacting to help him survive the Dursleys' treatment of him. While Harry has a somewhat decent relationship with them in the story, it's because Harry's transformation has made him too durable to really be hurt by them. Remember that a lot of Harry's dragon behaviors are unique to him: other dragons don't molt, they don't seem to have any hoarding instincts, and they can't eat almost anything like Harry can (and likely had to, since the Dursleys would restrict food for him). Harry may only have developed these abilities to survive his mistreatment. And in the case of his molting and hoarding, that may have developed because that was what he thought dragon behavior was like.
