Then there's Monty Python's "World's Funniest Joke" skit.
That's a clever way of looking at it (no pun intended).
I think it's also important to keep in mind that, by human standards, Medusans have extrasensory perception. It seemed to me that Kollos might have been telepathically sensitive beyond his interactions with Spock and Miranda. If Medusans really are telepathic, then what a being sees when looking at a Medusan might depend upon the experience of the perception itself. In that case, it would not be apt to discuss the appearance of a Medusan as if it were a static or fixed thing.