I am not sure if I have seen one, I might know one now but I can't be sure, excpet this person sucks ALL my energy out of me whenever we hang out. (Thus I am ending that friendship.) I have always been intrigued by the subject, but if they exist they are masters of keeping themselves hidden. Check David Icke for good hypothises, it kinda makes sense when you read about it. It's the same as speculation about aliens, we'll probably never know for sure.