Is the story of Momonosuke, the boy who transformed into a dragon, based on any folklore in real life? During the Punk Hazard arc, the boy Momonosuke transformed into a dragon. The story of a boy who turned into a dragon sounds really familiar to me for some reason. I believe I might have heard it somewhere before as some sort of tale, or maybe even as a part of some myth. I have been searching quite a bit to find something similar, but I couldn't find anything. 

So is the story of Momonosuke, the boy who transformed into a dragon, based on anything?
There are a couple of cartoons/anime/movies where a boy transforms into a dragon. 


American Dragon: Jake Long, an American cartoon.
The Chronicles of Narnia: The Voyage of the Dawn Treader, a movie based on the novel with same title, which has a boy who turns to a dragon.
Legend of the Dragon, another cartoon.
Fafnir, a legend connected to the idea of a person turning into a dragon:


  In Norse mythology, Fáfnir (Old Norse and Icelandic) or Frænir was a son of the dwarf king Hreidmar and brother of Regin and Ótr. After being affected by the curse of Andvari's ring and gold, Fafnir became a dragon and was slain by Sigurd.

A Chinese legend of carp turning into dragon after passing through the Dragon Gate.