BEHOLD! Apocalypto! The ancient paper bag thing that looks like Mimikyu!
Long ago, there was a world where spirits could take forms. There was one, however, who hated his form. That, my friends, was Apocalypto. He had the form of a wild pig with a grotesque face. After a while, he stuck his head in a paper bag he found. And he couldn't get it off. He grew fonder and fonder of the paper bag and kept it on his head. He soon became a long-living spirit of death, eating people's souls, explaining his size. Anyway, long story short, no one's actually seen what he looks like, so here he is now, buried in a desert, never to be approached by any mortal... ever again.