Teenagers who run away from home to live in the wilderness may become feral. As they become more and more feral, they gain some supernatural powers (a la Peter Pan - ability to fly, things they imagine come true - possibly quite powerful), but at the expense of their humanity and ability to speak, comprehend complex subjects, etc. Maybe they have a leader: the most feral of them all.
A regression into a fantasy childlike state.
There are reports of a monster that lurks in the tops of trees and drops down on unsuspecting people. It causes them no damage but it frightens them with a hide-like face with big dead eyes, drooling and barking like a dog while unsuccessfully attempting to have intercourse. The PCs investigate and find that it is the local village moron that is doing the spelunking in the woods. How can they explain this otherwise pleasant and merry man that it is wrong to put on a mask, drop down from trees and attempt intercourse with relatives and neighbours.