It has become quite the Internet rage.  I'm talking about flash mobs, where several or even several hundred people come out of nowhere in a public place and perform a choreographed song and dance much to the confusion then delight of the passers-by.  A new show recently debuted on Fox taking it to a new level with a proposal and wedding on the spot.  The flash mob craze has now come to the Tri-State.  At this weekend's annual Tri-Fest in Henderson, teachers from South Heights Elementary did there own flash mob performance.