The Doctor nods a little, not enquiring further, partly because of the potential spoilers, but mostly because he doesn't particularly want to discuss the Master, and she knows why.

"The metacrisis is here," he says suddenly, changing the subject, and picking the kittens off his shoulders and putting them in a chair. "Stay," he tells them, and it seems to work, before he turns back to the TARDIS. "And a friend of his who also looks like me, but.. cricket me."