19 things we learned from the set of the Doctor Who Christmas special

• Everything you need to know about the Doctor Who Christmas special
• There’s a subtle callback to Steven Moffat’s very first Doctor Who story in the Christmas special
• Pearl Mackie was originally not going to be in the Doctor Who Christmas special

Just consider it an early Christmas present from us to you – though that might make this first tease a little confusing…

1. There isn’t actually much Christmas in the special at all

Despite the festive occasion, as has been the case for the last few years this isn’t actually a particularly Christmassy episode of Doctor Who.

“Well it's snowy at the beginning,” episode writer and departing showrunner Steven Moffat mused, admitting “there's not a hell of a lot of Christmas in this one.”

And apparently the lack of too much festive cheer is down to the sheer number of Doctor Who specials from Christmasses past, meaning Moffat struggled to find anything new to say about the festive season this time around.

“I think it was a brilliant idea at the beginning and it lasted a very, very long time,” the screenwriter told us.

"I sort of think we might have mined and possibly over mined every single thing we could about Christmas in Doctor Who and the last time we more or less ignored it...

“[Now] it's kind of okay if you just try and make a decent episode, that possibly has some snow in it somewhere.

“I like there to be snow in Christmas specials, even though we all know it hardly ever snows Christmas day – except in Doctor Who where it does.”

However, David Bradley, who takes over the role of the First Doctor from original actor William Hartnell, hinted that there might be more Yuletide shenanigans than Moffat is letting on.

“It has a kind of link to Christmas,” he told us, “which is part of a thing I can't talk about.”

Curiouser and curiouser…

2. The Daleks are back!

Could the BBC really shoot Peter Capaldi’s final Doctor Who episode without including the Doctor’s deadliest foes?

Well, apparently not – because we learned on set that tin-plated terrors the Daleks do indeed play some sort of role in the finished story, though exactly how they’re involved (given that the episode’s villain has been revealed as a time-freezing glass woman) remains something of a mystery.

Just consider it another Christmas present that we’ll unwrap on the 25th.

3. Pearl Mackie wasn’t originally supposed to be in the episode

Despite her central role in the finished episode, it turns out that Pearl Mackie’s companion Bill Potts was originally left out of the Twice Upon a Time script.

“[Bill’s involvement] came to me later on actually,” Moffat told RadioTimes.com and other journalists.

“I was just starting into the script and we had Mark [Gatiss’s] character and we didn't have Bill and I was thinking, 'It's just proof of format again.' You need someone to whom to explain.

"Not to explain it to the Doctor; that's not what the companion does at all. The companion makes it fun.”

You can read more about this story here.

4. It was Peter Capaldi’s idea to bring back David Bradley to play the First Doctor

While it now seems like the obvious choice to bring back William Hartnell’s First Doctor through a David Bradley performance (he played Hartnell on TV in 2013, after all), the idea had to come from somewhere – and it was series lead Peter Capaldi who apparently lit the spark in Moffat’s mind.

“I was at New York Comic Con and someone was asking me about the War Doctor in [50th anniversary special] The Day of the Doctor,” Moffat recalled.

“I was talking about maybe the biggest contrast you could have between Doctors, because they are all the same person and obviously there is a limitation.

“I said, ‘Well the ideal one you want to do is William Hartnell meets the current Doctor, because that’s such a colossal difference; he's so different by that stage. Imagine how that lovely sweet old man, who isn't the least bit crotchety when you go back and look at him, would react to discovering he's this buccaneering space hero with the ego the size of a planet. How's he going to react? What's he going to say? But we can't do it because William Hartnell's dead.’

“Peter said ‘We can get David Bradley,’ and I thought ‘Oh yeah, actually we could. We could absolutely do that.’ So we did.”

5. Twice Upon a Time contains a subtle reference to Steven Moffat’s first ever Who story

As we have reported previously, the Christmas special features alien planet Villengard, which was mentioned in passing in the very first story Moffat wrote for the series back in 2005 (specifically in The Doctor Dances).

You can read more about this rather sweet Easter Egg here.