The special will also be "a great story of who the Doctor is when he's alone".
As Doctor Who fans prepare themselves for the long wait until Christmas, showrunner Russell T Davies has given some hints as to what we can expect from Joy to the World.
The new special has been written by Steven Moffat and will guest star Nicola Coughlan, and Davies has called it "one of the maddest Christmas specials you'll ever see".
Speaking in a behind the scenes video on YouTube for Empire of Death, Davies said: "Now the Doctor voyages forward, and guess what always happens to the Doctor every so often - Christmas! Here comes Christmas.
"I can't give away much more but work has begun on it already, and it's mad, it's one of the maddest Christmas specials you'll ever see. It's epic, it goes to so many different places. And it's a great story of who the Doctor is when he's alone."
Moffat, who was showrunner on Doctor Who between 2010 and 2017, returned to guest write the season 14 episode Boom which aired earlier this year, but has said he isn't returning for season 15 beyond writing the upcoming Christmas special.
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He previously told TV Choice: "I should probably introduce that one from an armchair, 'Here we are — number 50.' But I’m not involved in next year’s series. There are other things coming for me, so I might never write for Doctor Who again.
"As I got to the end of Joy to the World, I did think, 'Is that it? My final moment?' So that could be my goodbye. Number 50? I’ll take that."
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Moffat's previous episode, Boom, featured the surprise appearance of future companion star Varada Sethu, playing a character called Mundy Flynn.
While Mundy survived the episode, it is expected that she will play a different role in season 15 - although Moffat has teased a "plan" regarding her mysterious double appearance.
Doctor Who will return at Christmas on BBC iPlayer and BBC One. Previous seasons are available to stream on BBC iPlayer with episodes of the classic series also available on BritBox – you can sign up for a 7-day free trial here.
Check out more of our Sci-Fi coverage or visit our TV Guide and Streaming Guide to see what's on tonight. For more from the biggest stars in TV, listen to The Radio Times Podcast.
James Hibbs is a Drama Writer for Radio Times, covering programmes across both streaming platforms and linear channels. He previously worked in PR, first for a B2B agency and subsequently for international TV production company Fremantle. He possesses a BA in English and Theatre Studies and an NCTJ Level 5 Diploma in Journalism.
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