The Pope's memory. Awesome, just awesome. As cool as the story is, the movie is immensely cooler. The first scene in the movie is the end of the story. And each scene thereafter pretty much ends where the previous scene began.
Nothing is as it seems.
He has Poloroids of them, and he has written important notes to himself on those photos. To compensate, he takes Polaroid pictures of important things and writes himself little notes- who people are, what they mean to him, important things like that. It's the only way he can cope. If something is extra important, he'll have it tattooed onto his body. If you talk to him too long, he'll forget how the conversation started.