Christmas is a time for family, presents and holiday cheer. For fans of Doctor Who, it’s also a time of transition, when their favorite Time Lord is about to change incarnations.

Next Wednesday’s episode, “Time of the Doctor,” marks the third time in eight years that he faces a new regeneration during the holiday season. This time, fans will be saying so long to Matt Smith- who held the role for three years- and hello to 12, Peter Capaldi. They’ll be wondering how the transition will be done this time. The episode also faces the daunting task of living up to last month’s excellent 50^th anniversary episode, “Day of the Doctor.”

Not much is known about the episode, except that it takes place on a distant planet called Trenzalore. A mysterious force is calling the Doctor and Clara, plus some familiar bad guys including the Weeping Angels, Daleks, Cybermen, and the Silence. There’s also someone named Tasha Lem, played by Orla Brady.

Smith was interviewed by the BBC about his final episode. “The Christmas special for me is a bitter sweet episode because I’m leaving,” he said, “but Steven has written a brilliant, adventurous, funny episode and I’m really thrilled with it.  It feels wonderfully Christmassy.”

Smith also hoped that he would go out with a bang and a crash, at least. “I’m pleased it’s really funny and mad. When I got to the last 20 pages and it was quite a hard read for me, but I hope it’s going to be a belter,” he said. “We’ve got a great director in Jamie Payne and some really lovely double hand stuff with me and Jenna (Coleman). Steven (Moffat)’s managed to tie in plot points and narratives that have been threaded through over years and I think that’s ingenious.”

Smith also said it was an emotional experience filming his last episode, but at least one person didn’t want him to go. “My mother is mortified, honestly she was at the front of the campaign for me to stay and wasn’t happy when I said I was going to leave. But, when you’ve got to go, you’ve got to go. Of course, it’s very sad for me in many ways because everything is the last time. It’s the last read through, the last time I put on the bow tie and the last scene in the TARDIS. But the show is about change and I had lunch with Peter Capaldi shortly after the announcement and I think he’s just going to be incredible. He has the most brilliant ideas. As a fan, I’m genuinely excited to see what he’s going to do because I think he’s going to do something extraordinary.”

Speaking of Calpaldi, Jenna Coleman, who plays Clara, admits it’ll be a different show when the 12^th Doctor has his first episode next year. “We have a bit of a gap before we start filming the new series, so I have time to get my head around it all. Me and Peter will get together before Christmas to start rehearsing and the scripts will start coming in,” she says. “When I came in I think there was just a week off in production where Arthur and Karen left, so that would have been a strange shift. This episode is very much about Matt and the Eleventh Doctor and Clara and the Eleventh Doctor and their last adventure together.  I have no idea where we’re going next series!” The Christmas episode will reveal more of Clara’s home life, including her family.

Fans remember the last words of the Tenth Doctor, David Tennant, before he regenerated, “I don’t want to go.” Executive Producer and writer Steven Moffat was asked what Matt’s “final words” would be. “I didn’t think I would go that way,” he said, “but a couple of months before I wrote it I did say to Mark (Gatiss) that I thought I knew what his last moment would be, and indeed his last line. But if it didn’t fit the scene I wouldn’t crowbar it in. I’ve had the vague storyline in place for a long while.”

Some had said that Smith, at 26, looked too young to be the Doctor, but Moffat says Smith does “old Doctor” better than anyone else. “Because he was the youngest Doctor, Matt said, ‘he’s only got young skin. Nothing else is young.’ I think Matt makes you think very believably that he is this ancient being.”

Anticipation will soon shift towards the arrival of Peter Capaldi as the 12^th Doctor. At 55, he’s the same age as William Hartnell was when he originated the role in 1963. Moffat says they didn’t deliberately look for an older actor. “It wasn’t the reason I cast Peter but I do think if we’d cast another Doctor as young as Matt- because Matt’s been so good at being The Young Doctor- I’m not sure what another one would have done,” he said. “They’d have to have either been deliberately different or just repeat him.”

BBC America will air “Time of the Doctor” Christmas night at 9 PM Eastern and Pacific. Here’s a one-minute preview:

Before that, it will repeat “Day of the Doctor” at 6 PM, preceded by the six-minute prequel, “Night of the Doctor” with Paul McGann. That will be followed by a special on Matt Smith at 8 PM. For more information, visit http://www.bbcamerica.com/doctor-who