One of the things I've noticed about Tiana-as-a-human, after roughly one million enforced viewings, is that she sort of looks like a very pretty frog herself--her eyes are oddly skewed vis-a-vis the rest of her face, which is flat to begin with. But because she has those big, wide lips and that great smile, you don't really notice it so much; coloration helps, too (various shades of brown vs. various shades of green).