Moffat: "I've just written in a speech where [The Doctor] talks about the fact he doesn't have a hat".

Moffat: "You might think for instance, that there are things that live inside clouds. I'm just saying that kids, as a little nod to the future there".

Moffat has also dismissed 'rumours' that River Song is the same character as Amy Pond, and that River is the Doctor's mother.