Have you ever wondered how dragons can fly, despite their bulk? Or how they breathe fire? Or why they hoard gold? Author Peter Dickenson figured out an answer, and wrote about it in a book called The Flight of Dragons, which was later adapted into an animated movie by Rankin-Bass, made in 1982 and telecast in 1986.
At his website he wrote:
This one had a bulky body and rather stubby wings, which obviously would never get it airborne, let alone with the two people it was carrying on its back, and all its own weight of muscle and bone. Obviously any lift had to come from the body itself. Its very shape suggested some kind of gas-bag. I thought about it for the rest of the journey, and on and off for a couple of days after, and at the end of that time had managed to slot everything I knew about dragons – why they laired in caves, around which nothing would grow and where hoards of gold could be found, why they had a preferred diet of princesses, how and why they breathed fire, why they had only one vulnerable spot and their blood melted the blade of the sword that killed them, and so on – into a coherent theory that explained why these things were necessary accompaniments to the evolution of lighter-than-air flight.
His theory was interweaved with the story of The Flight of Dragons. See for yourself: