Global warming, the collapse of economies, nations stockpiling nuclear weapons. It's enough to make those who believe that the apocalypse is upon us pretty jittery. But pop culture gives us clues, too. David Hasselhoff still has the tatters of a career, and we all know who Heidi Montag and Spencer Pratt are. Maybe we need more pop culture signs that the apocalypse is nigh. What fourth horseman of the apocalypse will truly signal that the End Times are here?