What an amusing and interesting problem to have. My best guess, I don't actually know your players so just a guess, the first little bit will be rather goofy with plenty of lines delivered directly to the "camera," with a wink and a nod. However, as MoN begins to progress and the depth of the clues add up...and the body count rises, I think prior historical adventures are going to pale in comparison. Also, the idea of the real Sundance Kid being locked up in an asylum somewhere insisting upon being the real Sundance Kid...I mean isn't that what all the effort of being a Keeper is for?