Maybe a whole series where a different face shows up claiming to be the Doctor. In the end they all were, the timeline was a jumbled splintered mess.
Well, 11 did go into his own timestream after Clara, and she was splintered. The difference being each splinter Doctor then regenerated once.




he's the fly in the ointment, and obviously whoever is 13 might bear no relation to McCoy, but I do find the 4/5/6 10/11/12 comparisons interesting.