Bigfoot is one member of an advanced species, possibly alien that inhabit different locations around the world. All of these different creatures/beings possess an ability to cloak themselves from human detection. Their cloaking mechanisms normally shield them from all detection but from time to time, persons such as some faithful X-Files viewers who are especially attuned to the proper cosmic wavelengths are able to peer across the dimensional boundaries and glimpse them. Even more rare are those able to take images which even when shot under ideal photographic conditions are rendered fuzzy, grainy and motion blurred by their cosmic cloaking mechanisms.
While physically large, they possess an anti-gravitational ability that enables them to travel lightly without leaving tracks.
They travel longer distances aboard shiny saucer shaped transporters commonly called UFOs by humans. Their cloaking mechanisms normally shield their transporters from all human detection but from time to time, persons attuned to the proper cosmic wavelengths are able to glimpse them and even more rarely to take images which while filmed under ideal photographic conditions are rendered fuzzy, grainy and motion blurred by their cloaking mechanisms.
I heered they found a crashed WWII bomber on Mars wif Bigfoot daid at the controls! But it has been hushed up by NASA.