"I'm so thrilled to have been asked to guest in the Doctor Who Christmas special, I'm such a fan of the show," Frost said in a statement. "The read-through was very difficult for me; I wanted to keep stuffing my fingers into my ears and scream 'No spoilers!' Every day on set I've had to silence my internal fan boy squeals!"
Executive producer Steven Moffat said, "Frost at Christmas—it just makes sense! I worked with Nick on the Tintin movie many years ago, and it's a real pleasure to lure him back to television for a ride on the TARDIS."
The second name that jumped out is the recently returned to acting Michael Troughton (The New Statesman). The name Troughton is of course very familiar to Whovians as Michael's father Patrick Troughton played the second incarnation of the Doctor.
The cast will also include Natalie Gumede, Faye Marsay and Nathan McMullen.