Even by the standards of a show whose central character travels through time and space in a craft disguised as a ‘50s era British police phone box, 2012 has been an interesting year for Doctor Who, the BBC sci-fi series that stars Matt Smith.

Back in March, executive producer Steven Moffat announced that the Doctor’s new assistant (or “companion”) would be played by Jenna-Louise Coleman and that the British actress was set to make her debut in this year’s special Christmas episode, which BBC America is screening on Dec. 25 at 9 p.m. So Who fans were taken by surprise when, this September, Coleman appeared in “Asylum of the Daleks,” the first episode of the current season of Doctor Who, which also starred the Time Lord’s now (dearly) departed companions Amy (Karen Gillan) and Rory (Arthur Darvill).

More bewildering still, Coleman didn’t seem to be playing the role of the Doctor’s new companion — whose name we now know to be Clara — but rather a character named Oswin Oswald who had been converted into one of the dreaded Daleks and who seemingly died at the end of the show.

In the new issue of ENTERTAINMENT WEEKLY, Coleman talks, exclusively, about keeping her role in “Asylum of the Daleks” a secret and when fans might get some answers with regards to the Oswin/Clara conundrum. Below, the actress, whose previous credits include the Julian Fellowes-penned Titanic miniseries, ruminates further on these subjects — as well as discussing the forthcoming Doctor Who Christmas show and revealing where Karen Gillan recommends you should eat next time you’re in, uh, Cardiff.

ENTERTAINMENT WEEKLY: You surprised pretty much everyone with your appearance in “Asylum of the Daleks.” Who did you tell about that ahead of time? Were you allowed to tell your family?

JENNA-LOUISE COLEMAN: Yeah, my family knew. But I was convinced it wasn’t going to be kept [a secret]. I thought maybe at least we could keep the ending a secret, with the Dalek. It’s just great. There’s not much TV these days where you really get that element of surprise. There are so many spoilers all the time. I was really shocked that it didn’t leak and so was Steven. We were all really pleased and proud about that.

The role of the Doctor’s companion is so important to the show and such a plum part for an actress. What was the audition process like?

Well, I had my first audition with Andy Pryor, the casting director. Then they brought me back to read with Matt before Christmas and then I had another session with Matt after Christmas. So it was three all together — but it was lovely, actually. [Eventually] I think there were six people there — producers, casting directors, and everybody — and they actually left the room and left me and Matt to it. I’ve never had that in an audition before. They let us play about and made the scene our own and then they all came in to watch.

How did you find out the role was yours?

My agent phoned me up about two days later saying I’d got the part. I was in [British department store] Marks & Spencer. I couldn’t carry on shopping. I had an avocado that I had to put down and just went for a walk.

I’m still kind of digesting everything. The Doctor Who Experience (a permanent, Who-themed exhibition) has just opened in Cardiff and I look out my window and see it and it’s so huge. I came out to L.A. not long after I got the part and so many people out there were talking about it. It’s still becoming real to me in a way.

I believe Matt Smith had never seen an episode of Doctor Who when he auditioned. Were you a fan? It wasn’t actually on TV when you were growing up.

Well, we missed it! We missed it! And then when it came back in 2005 I was, like, 18. I was aware of it but I kind of missed it. I didn’t really know anything going into the audition room, which was kind of nice. I didn’t know what Matt was going to throw at me because I wasn’t used to it. Obviously I was aware of him but it was kind of new too me.

And then I didn’t watch too much of Karen and Matt’s stuff on purpose because it’s such a rhythmic thing, the dynamic, that I don’t want to pick up on anything. I kind of want to research it and watch every single episode, but my character, I’m just a girl who’s going into this not knowing anything and has to experience it front on. So that’s what I need to do as well, I think. And that’s what Steven’s very keen for me to do.

My grandma is a huge fan. My auntie was over from Australia when I got the part and she used to hide behind the sofa from the Daleks. My family — it was kind of like every single generation [except me]. It was quite strange, though — as soon as I started auditioning, when you actually look, Doctor Who really is everywhere. I turned up at the BBC for my audition and I was eating my lunch and I looked up and there’s a life-size cutout of Matt just staring at me.

I was recently talking to someone on a plane and, after I mentioned that I was writing about Doctor Who, they not not only declared themselves to be a fan but then explained at some length why Christopher Eccleston was the best ever Doctor.

Yeah. It’s the magic of it, isn’t it? It’s generational and universal. My friend’s little brother, who’s only like 7, is a massive fan. He’s got his own little TARDIS in his room. I see little kids dressed up as [the Doctor] and then my grandma is the most excited person in the world as well. I don’t think there’s many shows that have it, that cross so many generations.

Next: The problem of playing a Dalek

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Amy and Rory were so beloved. Has it been daunting to fill their shoes?

It’s strange, actually. I watched the five episodes that went out recently as we were filming. It was strange to watch their goodbye as I was doing the beginning — and interesting to see where it left the Doctor as well. There’s no way to consider it other than something totally different. You fill somebody else’s shoes by trying to do the same thing — and I don’t think that’s a healthy way to look at it. It’s a whole new story, it’s a whole new character. It changes the Doctor and you’ve got to go on that journey and also go on your own journey with it, as well.

Is it true Karen Gillan left you a note?

She sent me a message. She texted me. I was pacing around, trying to figure out a scene and I checked my phone and I just had a message from her saying kind of “Good luck” and “You’re going to knock it out the park.” Then she told me eat at Woods restaurant in Cardiff. That was her Cardiff tip.

Matt Smith has been on the show for a few years now. What’s it been like working with him?

He is awe-inspiring. His work ethic just knows no bounds, really. It’s a work in progress and every day is something new and he’s incredibly creative and I feel like I’m learning more and more from him.

But in “Asylum of the Daleks” you were pretty much on your own in a room. What was it like acting with nobody?

That was really interesting. That was one of my huge concerns. The idea is you’ve really got to feel the banter and the dynamic between Oswin and the Doctor and I was really concerned about how that was going to work without Matt being there.

Basically I had a screen with a green circle in the middle which I spoke at for two days. So that kind of did help with [not] losing your mind. But Matt came down on my first day and we ran some stuff together so I could kind of get the feel of where he’d pitched it so it could really sync together. I’d seen some of his rushes as well. We did what we could to really sync us together.

“Asylum” was so funny but also so very sad.

That’s what Steven is so beautiful at. That’s the thing — it is so light and you can play so much with the comedy and he never over-sentimentalizes anything. But, reading that script, I found it so heartbreaking, the end.

It’s interesting actually — I think I can tell you this — that that was never the initial plan either, to have me be Oswin. That was part of a genius plan that Steven came up with half way through the audition process. That was already written but not written for what was to be the new companion. I was auditioning for the companion and then I got all these sides and I was like, “Who’s Oswin? They clearly don’t know what they want, they obviously don’t know what they’re looking for. They just want people to show them different things and see.” This is what I assumed when I was auditioning, not realizing that it’s basically Steven’s mad genius again.

So, you played an ultimately deceased Dalek on that show and now you are about to debut (again!) on the special Christmas show as the Doctor’s assistant. All of which obviously raises about a thousand questions. Is this a subject that is going to be addressed in the Christmas episode?

Uh… mmm… no. We’re going to have what has been referred to as a “soft mystery.” For me, filming, I’ve been totally oblivious to Oswin and the “Asylum of the Daleks.” I really have had to erase it from my memory. Yeah, Christmas is it’s own episode.

Oswin was a Dalek. Can you tell us whether your companion is human? Not all of the Doctor’s companions have been.

That’s why it’s so difficult [to talk about it]. Because of the way it started with Oswin, it’s really difficult to say much: where she’s from, what period she’s from, what planet she’s from, even.

It’s not often an actor can’t even reveal what planet their character is from.

Exactly, yeah. I know. Doctor Who’s the worst for it, isn’t it?

What can you say about the Christmas show?

I feel like I’ve been in Christmas for about six months. [Laughs]. We’re still finishing up on ADR and things at the moment. There are some absolutely stunning, beautiful, very magical, magical, magical, moments in it that’s Steven written. And it’s very icy and snowy.

Do you at any point say, “It’s bigger on the inside!”

You’ll have to wait and see.

You can check out the trailer for the special Doctor Who Christmas episode below.