"Doctor Who" will be saying goodbye to two of its vital cogs, current Doctor Peter Capaldi and showrunner Steven Moffat. The science-fiction show produced by BBC tells the story of an extraterrestrial being called The Doctor who travels through time and space helping people in need. This send-off will happen on the show's Christmas special and fans are excited to see the Twelfth Doctor's regeneration.

The episode will be tilted "Twice Upon a Time" and will be shown to have two Doctors both refusing to face their respective regeneration.

Once the regeneration is done, Capaldi will be replaced by actress Jodie Whittaker as the Thirteenth Doctor; she will be the first female Doctor in show's long history.

In an interview with Empire Magazine, Capaldi talked more about his regeneration, saying, "I couldn't have wanted for a more moving and emotional end to my time as Doctor Who. It was strange to shoot that scene but in a way, you've been practicing all your life to collapse on the floor of the Tardis."

Reports surface that BBC has asked former Who companion Jenna Coleman who played Clara to come back one last time to reprise her role. The actress is currently starring in another TV show "Victoria" and no confirmation has been made. It would be remembered that both Karen Gillan and Billie Piper who played former companions Amy and Rose, respectively, appeared in cameo roles when their own Doctors left the show. Pearl Mackie, who is the current companion of The Doctor, will come back as Bill and will appear alongside Mark Gatiss.

Showrunner Steven Moffat said that for this Christmas special, they will be going the extra mile to recreate the image of the First Doctor in telling the story of the Twelfth. He further added that they have added new monsters and the meeting between the First and the Twelfth will be something to look forward to. The episode will air on Christmas day and after the Christmas special, the new season of "Doctor Who" will be helmed Chris Chibnall.