The Mansion has a library, which, as we know, possibly rivals the Unseen University's for content if not for size. A lot of books, basically; a lot of stories. And some stories, because this sometimes happens, have gathered different versions of themselves over time. Which wouldn't normally pose a problem, except now the room's been tampered with. And if one were to walk through at this point, one just might find oneself in the wrong version, or maybe even the wrong universe altogether.
T: AU crackplot, with the corollary that if one's puppet has alternate canon -- anything at all from mythological mess like the mass of Arthuriana to "sequels" like Mr. Darcy Takes A Wife -- they get to switch over to one of those for a bit. If they don't, or you don't feel like it, there's always your standard AUs instead.
And since this was at typist request,
bigbroroxxors can totally consider this our first offensive in his war. :D