What if the 9th Doctor never regenerate. What if he did all the 10th and 11th Doctors adventures. (Beside the 50th anniversary special.) He drop Clara home and never return. He then travel to Equestria. But he regenerate into an dragon egg after fighting the Cybermen and lost his memories.The egg was discover by Princess Celestia and hatch years later by Twilight. What if Spike was the egg and been regain those memories after Nightmare Moon return.
(Looking for an editer and cover image)