Apocalypse Cow
A beast that has been around since the dawn of time. It is the embodiment of all end-of-the-world prophecies past, present, and future. Its "moo" is a siren's call that leads the gullible, stupid, and ignorant to drink the kool-aid of its teats, hypnotizing them to believe that "judgement day" is closer than it actually is. The hypnotized are so certain of such "imminent" doom that it becomes a self-fulfilling prophecy and they even try to manufacture such apocalypses.

The name comes from the fact that every religious cult has been milking the end-of-world scenario since crawling out of their caves.
Nut: It's May 21, 2011! THE DAY OF DESTRUCTION IS UPON US!!!!

Sane person: Someone's been suckling on the Apocalypse Cow's teats again.