I've been rereading
Grave Peril and I've had my interest piqued by the idea of pocket universes in the nevernever. We see it with Agatha Hagglethorn's Chicago and there is mention that some really powerful dreams can generate their own reality, too.
So it got me thinking, if some dreams can generate their own reality, why not really strong imagination. What if a single-minded focus, dedication and attention to detail along with the collective imaginations of millions has created its own reality in the Nevernever- say like a Middle Earth.
Really, though it could take the form of any story (book, movie or anything else) that you wanted!
So when the DFRPG comes out, I'm going to be asking for some help statting up a Balrog to toss at my group when they begin their trek into Moria