And the troll doesn't look right, and doesn't look right, with that nagging not-quite-right-ness at the back of the brain, and the face is just not right, and I slave over it and slave over it and draw and erase, and finally I move the nose up a centimeter and change the shape of the head a bit, and make the eyes longer and suddenly it's fine. It's a troll. It clicks into place.
I find this amusing, because the trolls that look like this are things I whipped up in frantic preparation for a convention two years ago. They could have looked like anything. And yet, between then and now, this personal creation became cemented in my brain. Somewhere, stamped hard, below the conscious level, my brain KNOWS what a troll's proportions are, and knows them well enough that when they're off, it does the same something-isn't-right-here itch that it does for human figures. (And occasionally real humans. Ever met somebody whose ears are set really really high on their head? There was a bit actor in some made-for-TV-movie years ago that had really high ears, and I was going crazy trying to figure out why the guy registered as so strange, when he was otherwise fine looking, and finally realized that his ears were set a good inch above the norm. I swear, you never realize how low or long ears are until you draw them...)
The fluidity of what humans will accept as normal in other humans is vast--James, for example, has a lazy eye, which I have not actually noticed for the last decade (although I think it may also have lessened with age.) But I find it funny that the opposite holds true, and a minor creature I made up myself now has a sort of proportional canon in my brain and I deviate from it at my peril.