If you go to the A Book of Creatures website, you can find dozens or hundreds of monsters and crypids described in detail, and some of the details just make you itch to run a fantasy RPG specifically so you can put them in there. A while back, a very brief post presented “Another alpine dragon… What really sells it is the melodramatic look of dismay on the guy. That or he’s yodeling to it.” [emphasis mine]
And for some reason that one-off comedic aside is what fired up my imagination the most. I want a campaign with a fearsome monster – a tatzelwurm guarding a mountain pass, for example – that will leave you untouched if only you sing to it the whole time you’re within earshot. Imagine sticking that on the map, letting the PCs encounter it and get routed like Monty Python’s grail knights versus the beast of Caerbannog, and then have their minds blown when they realize that local farmers, who of course know the wurm’s secret, walk right by it every day without a care.