Myth or the real thing?

I am sure by now everyone has heard stories such as unicorn, Bigfoot, fairies, and much more. We all wondered if either one of them ever did exist at least a long time ago. Though sometimes these myth can only be things we normally see everyday that accidentally gone through some event and accidentally create a myth. This is only the examples I come up with so please do not consider this as a fact. For example an owner of the horse someday crafted a horn-look alike and stick it on his/her horse. Other people saw the horse and assumed it was a mythical creature or so. Like I said, this is only examples I thought through and it may be incorrect in some way.