I'm leaning towards Kinder-Fresser, if you're asking for input. After reading over the descriptions at the links, it's the only one that doesn't seem impossible or silly. And the papstesel is seriously messed up. It *might* be fun, but describing it would take up so much space!

Oh, and the Kinder-Fresser seems like a great monster to have in a story about a homeless teen. ;-)