Moffat's plan:

Moffat:
I've got a plan.
Lackeys:
Ok.
Moffat:
Get an actor from Sherlock.
Lackeys:
Ok. We follow.
Moffat:
Then an actor from Harry Potter.
Lackeys:
Ok.
Moffat:
Put them in to Doctor Who.
Lackeys:
Ok. Then what?
Moffat:
Watch their tiny little brains explode.