Comment on MLP- Skeleton anatomy doodle by EarthnAshes

It is possible for a unicorn to have a curved horn, but it's uncommon. If they do end up having one, however, the curve isn't nearly as noticeable as an Alicorn's, specifically, a naturally born one (Twilight's a special case). And if it happens, it isn't through anything bad or nothing; it's mostly just a harmless mutation to the horn's bone structure that gives it its curved appearance.