It's time for the festive edition of our favourite sci-fi show, and this time, we're waving goodbye to Matt Smith. After an incredible stint at the controls of the TARDIS, it's time to bid farewell to Smith, and welcome in Peter Capaldi. This Christmas special should be emotional, but here's the official blurb: "Orbiting a quiet backwater planet, the massed forces of the universe's deadliest species gather, drawn to a mysterious message that echoes out to the stars. And amongst them, the Doctor. Rescuing Clara from a family Christmas dinner, the Time Lord and his best friend must learn what this enigmatic signal means for his own fate and that of the universe."