I’m So Thick! (series 7 finale spoilers
In The Name of The Doctor, when the GI was confronting Vastra and Jenny and Strax, he said the Doctor would be known by many names before the end of his like. One he said was “The Beast”
The beast said he came before the universe. Meaning before the Big Bang,
this idea has been driving me mad lately
So the Doctor created the universe we are in right now, (Pandorica, etc…) so he had to come before it.
The Doctor becoming The Beast would also explain why he knew so much about all those in The Impossible Planet. But wait. the Doctor died at Trenzalore, well yes and no. We don’t see a body. He could die, but partly regenerate somehow, so his consciousness is split. His good dies, (the blue scar tissue, it turns red once evil is entered) And the Evil one goes on to become the Beast. But the Doctor’s companions would’ve stopped him and locked him in a prison around a black hole.
Well, its just a theory