The casting of Michael Gambon for the special certainly was a great casting coup, and when asked how he managed to get the great actor on board, Moffat said:
We sent him a script, asked him to do it, and he said, ‘Yes.’ Simple as that.Steven Moffat also said that he didn't know if the Harry Potter actor was a fan of Doctor Who per say, saying :
I don’t know, I didn’t get the impression that he was a fan of ‘Doctor Who,’ except insofar as everyone in Britain is at the moment, but it’s really…with these guys, send them a good part and there’s a really stonking chance they’ll do it. I mean, if it’s a good script…and you think it is…they’re being offered prime-time on Christmas day, really, so there’s a real chance you can get anyone for that. But it’s very exciting. He’s brilliant. Of course he’s brilliant. Absolutely brilliant. What a voice.When pried to specifically reveal a few things about the Christmas special like that 'Orient Express in space' line that was mentioned by Matt Smith's Doctor in the final episode of series 5, Moffat made a very funny revelation:
You wouldn’t really want to know, I can tell. Also, what you have to keep in mind that I genuinely lie. I do. I actively lie to people about what’s going to happen in ‘Doctor Who.’ I’m not officially employed with the BBC. I can say any old thing I like. Even if I told you something, there’s no guarantee that it’s true. Disinformation and the white noise of nonsense is how we get through this![Premium Hollywood]
It was a well-known fact that Russel T Davies, the previous showrunner, had been in the habit of doing the same thing, giving disinformation about the show. He even admitted it in his book The Writer's Tale, so no surprise at all here that Moffat is doing the same thing.