I'm kind of surprised that I haven't seen reference to the piece of paper that drops from above (offscreen) onto the TARDIS console right before the cut to next week's preview. If I missed reference to it here or in another thread, my apologies.
Any wild speculation? Note from the TARDIS? Perhaps the TARDIS dropping a page ripped from the History of the Time War (the one referencing the Doctor's name) so that Clara won't find it again?
That isn't a piece of paper that's the rag the Doctor was using to wipe the console (and smack Clara on the bottom!). It's not even offscreen you can see him hook it in the air.