Space Rabbit
Space Rabbit emerged from the primordial ooze 3,896,743,886 years before the common era in what is now an area under the ocean between Australia and New Zealand. At that time, all mammals were monotremes, and so Space Bunny began as a very, very big egg. Nipples were yet to be invented, so when it hatched, it fed off the free floating archaea.
Born albino, like all laboratory rats, the radiation from a supernova caused it to turn an odd sort of pinkish-purple, gave it super nostril powers and changed its eyes from pink to brown. French anthropologist and antique motorcycle enthusiast Marcel Marceau has advanced a theory that Space Bunny moved backwards through time as a result of mutations brought on by irradiation. This resulted in the Punic Wars.
As a youngster it contracted the usual childhood diseases, as well as picking up a really bad case of ear mites. There are many cults based on mites proliferating throughout the Siberian tundra. Sleds in the shape of giant mites were pulled by wooly mammoths up burial mounds of kings to offer sacrifices of dandruff to the mighty mites.
During adolescence, Space Bunny retreated into its shell, breaking the very chains that bound it to the Earth. Since the Moon was much closer at the time, fading gravitic waves and pulses shuffled the monstrous carcass into interstellar space, coming to rest 17 light years perpendicular to the galactic plane.
When it reached adulthood, Space Bunny returned to Earth, and was repelled by the Space Greeks in 2416 after the common era. Its insatiable hunger for planets had, by this time, gained popular acclaim. Nevertheless, the more sapient among humans and abhumans wisely decided to invent a weapon using so-called dark matter to cast the great beast into the bowels of Hell.