I have, and it is quite true. Regarding the Monsters Inc monsters, however, I think the cue is not only that they don't look human (they look like big bears &c), the parts of them that do (as you say, smiles) are right, while smiles have the power to unsettle if they are wrong and on something that looks human, having one on a big blue bear (fuzziness helps) merely makes them relatable. I think all their eyes are big as well, regardless of number. For some reason that has the same effect (but only in drawings -- similar eyes in a realistic-looking film would scare me silly. Perhaps the divorce from reality that a drawing entails punctures the uncanny by removing it too much (or, rather, enough) from reality.