. . . Was that in character?

"Oh yes, in character, I did feel like a 12 year old! Also, the actual idea of being part of the Doctor Who family and being asked back, not once but twice. The camaraderie of the team was lovely, the script read-through around the table, getting into the frock! The other thing was getting to meet lots of other actors: Neve McIntosh was lovely to work with… Mark Gatiss..."

Amazing, is he in Episode 7 or Episode 13?

"That’s Episode 13."

Source credit goes to Doctor Who Spoilers.

Already the only person to have appeared on-screen and scripted episodes of the series, including "Victory" and "Lazarus", Gatiss's return may come as a shock to viewers. His previous role as the titular Professor Lazarus ended with the character's monstrous death. But with the well established insanity of the Series 6 finale, an alternate Lazarus could be one of the most tame aspects of the episode.

His Series 6 episode already completed, Mark Gatiss is discussing his productivity last year.

I had a bit of a mad year, to be honest, and was sick of the sight of myself by Christmas, so God knows how everyone else felt. In my defence, scheduling is a curious beast and it fell out that two things I'd made the previous year (The First Men in the Moon and Worried About the Boy) ended up being shown slap-bang in the middle of my History of Horror documentary series for BBC4. On that subject I must take this opportunity to record how fantastic it is that there's still a place where a passion project (as that series most certainly was) can be so championed and encouraged. Equally, that documentaries as startling and oddly moving as The Young Ones and as rich and strange as The Dancing Boys of Afghanistan still have such a valued place. 

Speaking of scheduling, it's worth saying that when Sherlock was scheduled to air in the traditionally dead summer slot it seemed like very bad news. It's a measure of how differently we now watch shows that this didn't prove to be the case. Whether catching up on iPlayer, recording on our Sky boxes or downloading our favourites, overnight ratings are ceasing to have any meaning. But you mustn't get me started on ratings or I'll start singing "The King is in the Altogether" and we'll be here till Christmas.

Source credit for the above quote goes to the Doctor Who News Page.