5L1 - The Horns of Nimon 1

Apart from Episode 7 of The Daleks' Master Plan, The Feast of Steven, which went out on Christmas Day 1965, the first official Christmas special in Doctor Who was 2005's The Christmas Invasion, beginning a yearly custom that has become an annual tradition. We are all forgetting, of course, The Horns of Nimon, which is the closest Doctor Who ever came to full on pantomime in the show's long history.

Everything about this story is high camp. Look at the pilot of the ship taking the tribute from Aneth to Skonnos. He's played by an actor called Bob Hornery, who actually hasn't appeared in much over the years, but is the type of actor who looks like he may have at one time. You almost feel embarrassed for him, wearing his costume with wild shoulder pads and crazy triangular ornaments on his chest and helmet, forced to shout lines like "Blundering fool! You've wrecked it!". If Ian McKellen ever did panto, it would look like this.

And then there's the Anethans themselves, weakling scum that they are, dressed in bright yellow pajamas that make them look like the kids from Peter Pan, flying away on a magical journey to some dark and foreign land. And this is all within the first five minutes! That's not even mentioning the scene where The Doctor gives K-9 mouth-to-mouth resuscitation. That's not even mentioning the costumes worn by the Skonnons (and particularly Sorak). That's not even mentioning Soldeed...