くねくね (Kune-kune, an onomatopoeia meaning "wiggle-waggle") is an urban legend that has been going around the Internet since 2003. In this scary story appears an unidentifiable being.
Although the story has a number of patterns, the most representative storyline is the one where "the narrator wanders around the countryside in the summer, near a paddy field or a river, and sees a white thing that wiggles its body in a manner far different from that of any person or living creature. He asks his companion what that thing might be. His friend uses binoculars in order to verify the actual shape of the thing, and as soon as he understands what it is, his mouth seizes up with fear and he becomes insane."
The locals know that "when you see the wiggle-waggle, once you understand what it is, it has an abnormal effect on your soul," and they regard it as taboo. In the stories, sometimes there can be a warning from the local elders who say "if you see such a thing, you should not get close; you should quickly forget you ever saw it."
Not to be mistaken for the visually similar Hattifattener from The Moomins.