Aside from a metaphor-heavy Jewel song, stories about people and beasties swallowing the moon pop up all over mythology. Certain Native American peoples believed that a giant cod was the culprit; others, a spirit of sorts. In China, it was a toad.
Norse myths are adamant that it will be a wolf. Because the Norse like to go that one extra step, they make clear that, at Ragnarok, the wolf will succeed in gulping down the moon, spattering the heavens with blood.
They cannot, however, agree which wolf it is, bickering back and forth that it will be Fenrir (also called Fenris) or his son Hati who is sometimes called Mánagarm. Frustrated that they can't even agree on a single name for even one of the giant, world-ending wolves, they then escalate to hitting each other over the head with massive, short-handled hammers, because...well, they're Norse. So, here is my wolf/frog/fish/spirit, having just succeeded in swallowing the moon which shines out from behind his ribcage. I'm not sure what he plans to do with it next, but I doubt it will be pleasent. Maybe cause an eclipse.