Trained as a Scientist, I find a lot of fantasy utterly hilarious as lacking in 'rigour'. Okay as 'light relief', but plausible as a 'Road Runner' Toon...

A surfeit of vampire tales of the 'transmogriflying' variety exasperated me enough to do a 'deconstruction' of the genre: Applying Clarke's 'Third Law', they're hyper-nimble, night-hunting, obligate carnivorous cryptid hominids, whose extreme porphyria got locked-in by genetic bottleneck when their now-mythical 'day-walker' cousins were exterminated by braw, Bronze-clad warriors...

;-)