Pokedex: "When exposed to the moon's aura, the rings on its body glow faintly and it gains a mysterious power."

"The hare appears in English folklore in the saying "as mad as a March hare" and in the legend of the White Hare that alternatively tells of a witch who takes the form of a white hare and goes out looking for prey at night or of the spirit of a broken-hearted maiden who cannot rest and who haunts her unfaithful lover. In Irish folklore, the hare is often associated with Sidh (Fairy) or other pagan elements. In these stories, characters who harm hares often suffer dreadful consequences.

Many cultures, including the Chinese, Japanese, and Mexican, see a hare in the pattern of dark patches in the moon (see Moon rabbit); this tradition forms the basis of the Angelo Branduardi song "The Hare in the Moon"." --Wikipedia

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I've always liked the idea of Umbreon being based on a hare rather than on the typical fox- or cat-like creature. I'm just a big fan of folklore like that. :'D

Note: This one really looks a lot better on my DA page since I don't think FA likes transparent backgrounds too much.