Although Christmas is five month aways, news of the Doctor Who Christmas special is already being either leaked or details being given away. The official BBC tv trailer for the episode has been released and its below. This may contain spoilers so look away now. For those who watched the end of the last episode, the 1st Doctor makes an appearance. The 1st Doctor is to be played by David Bradley who played William Hartnell in a drama about how Doctor Who got started. The Wintery landscape is a nod to The Tenth planet in which the Cybermen first appeared. In the original Tenth Planet, the Doctor disappeared and this is going to explain where he went.
There was a rumour that Clara Oswald would be appearing in this Christmas episode but there's no shots of her. We do see Bill Potts somehow back as a human. In the last episode, she had been converted into a Cyberman and then last seen turned into a water creature.
At the end of the episode, we do know that the Doctor will regenerate into a female for the first time in its history. The decision has split fans, some for, some against and some wait and see.
Its not the first time a character has changed genders, if you can remember back to the 2003 Battlestar Galactica remake, two of the main characters from the original series became female. They were the wise-cracking Lt. Kara Thrace ( Starbuck ) and Lt. Sharon Valerii ( Boomer ). It didn't seem to that series any harm so lets just wait and see before we start "rioting".