Abominable Snowman

You haven't seen one, but you insist they exist because you've seen their tracks. Ideas of this sort are like the AbominableSnowman. You might recall that even Hillary discovered AbominableSnowman tracks up on Everest. Great big bipedal tracks, clear as day. Except that they discovered later these tracks are actually made by mountain goats leaping through deep snow. The goats spring up into the air, then land with all feet together. They leap diagonally across their axis of forward motion. After a day's thaw and a night's refreeze, the result is AbominableSnowman tracks.