In Germanic mythology, Skoll was a wolf that pursued the sun in her flight across the sky. At Ragnarok, the event that signals the end of the world and the doom of the Aesir, Skoll was destined to finally catch that pesky sun in its big ol’ jaws and swallow it. You devious, sky-wolf! However, just before the swallowing, the sun would give birth to a daughter as beautiful as herself, and this shiny new sun would warm and illuminate the new earth, fresh ‘n green, risen from the sea after the catastrophe.
Another wolf, Hati, chased after the moon, and both Skoll and Hati were said to be the sons of a giantess.
Ravenous dogs often threatened to eat the heavenly bodies in the myths of northern parts of both Europe and Asia. Chinese families today still bang cooking utensils to frighten “the dog of heaven” during the lunar eclipse. The sun and move needed a reason to haul-ass across the sky, I suppose, and what better reason is there than being chased by a hungry mega-dog?