In an interview with the Radio Times, Walters said: "You can't beat being in Doctor Who - it's something I've grown up with my whole life and working with Matt Smith was amazing. He's a really, really good actor and just being a part of that huge BBC franchise was an incredible thing. And Jenna Louise Coleman is really good at what she does - it seems like she's enjoying her job and I loved working with her."
"I nearly got sacked on my first day because they're really strict about it. I was in my costume lying down on the sofa and I just tweeted a photo with the word 'space' - I didn't say anything else. Five minutes later I had execs knocking on my door saying, 'what are you doing?' And then I realised there were signs everywhere saying 'don't tweet'."
However, the actor did reveal some episode details: "In our episode it'll be the first time people get to see so much of the Tardis." The story is heavily rumored to carry the title Journey to the Center of the TARDIS.
(Source: Radio Times)