Planet X is a (hoax) planet that is supposed to visit the Earth in 2012 and cause a global catastrophe. Its orbit is unlike the rest of the planets so it is only within our normal planetary range periodically.
2012 is just another of a string of dates that is supposed to bring the end of the world as we know it. As far as I know planet X has no real scientific data to support it and therefore I wouldn't worry about it.
You say it's real?!?
Ok, ok I know some folks take this Planet X business quite seriously. In light of this fact I would like to ask any out there who do believe in Planet X, why?