Peal Mackie, who plays companion Bill Potts in the sci-fi drama, has revealed that the episode will be “hilarious” as she unveiled the latest trailer on Sunday Brunch.
The 30-year-old actress was asked to sum up the special without spoiling any secrets, and she revealed that the relationship between Peter’s 12th Doctor and David Bradley’s incarnation of the first is something to look out for.
She said: “There’s two Doctors – well three Doctors in it, technically, isn’t there? You’ve got Peter as the 12th Doctor who is struggling with not wanting to regenerate and he meets the first Doctor, played by David Bradley, who is absolutely amazing.
“The dynamic they have between the two of them is so funny. It’s amazing. Their dynamic together is absolutely hilarious.
“It’s a lovely episode and it’s Christmassy, and there’s snow, and there’s two TARDIS’s, and I’m in it! It’s very exciting.”
Each Doctor will then try to convince the other to regenerate into their next incarnation, meaning viewers are likely to then see Patrick Troughton’s second Doctor in some form, along with Jodie Whittaker’s 13th incarnation.
Actor David, 75, teased that there will be a clash between the pair, but they will gradually earn mutual respect for each other.
David previously explained: “The 12th Doctor is rather shocked by this old guy with his 1960s sensibilities and his non-PC attitude to things.
“For me, the comic energy between them is a lot to do with the two different worlds they’re coming from, but gradually there’s mutual respect and, by the end, acknowledgement.
“At one point Peter and I looked at each other and I wondered who was going to well up first!”
Doctor Who returns to BBC One on Christmas Day at 5.30pm.