Before we get into the actual episode itself, a word about the two prologue mini-episodes. One shows Madam Vastra wrapping up one of her criminal investigations - a convoluted tale which is clearly inspired by one of the more complex Sherlock Holmes stories, or more likely one of Dupin's (Edgar Allan Poe's detective from The Murders in the Rue Morgue (1841) and others).
The other is the one where the Paternoster Gang attempt to lure the Doctor out of his self-imposed exile.
They each tell him about a potential threat which might pique his interest. These are all inspired by the fantasy works of Jules Verne / HG Wells / Edgar Rice Burroughs / Arthur Conan Doyle.
Strax talks about the "Moonites" - as in the Selenites from The First Men in the Moon (Wells, 1901), or George Melies' film A Trip to the Moon (1902), based on Verne.
Vastra mentions a meteorite shower, hinting at possible UFO activity - Wells' War of the Worlds (1898).
And Jenny warns of a scientist who is going to drill into the centre of the world and possibly split it apart. As well as a nod to Prof. Zaroff of The Underwater Menace, this also points towards At The Earth's Core (Burroughs, 1914), or When The World Screamed (Conan Doyle, 1928) - in which Professor Challenger attempts to drill into the Earth but wakes up a vast monster dwelling deep beneath the surface.
Jenny also mentions a man in Praed Street who has an invisible wife - referencing Wells' The Invisible Man (1897).
The obvious starting point for The Snowmen is that this is a sequel to two highly regarded stories of the Patrick Troughton era - though it come in the form of a prequel.
In Season 5 of Doctor Who we were introduced to the Great Intelligence - a malignant, disembodied entity which sought to build a bridgehead in a remote part of the globe (Tibet). It psychically possessed a human being to act as its agent on Earth, and used deadly robot copies of local wildlife to keep anyone who might interfere away - or indeed to dispose of them all together.
These creatures were the Yeti, who became known in the West as "Abominable Snowmen" purely thanks to a mistranslation by a journalist.
So pleased were the production team with The Abominable Snowmen that they commissioned a sequel before the initial story had even broadcast. This moved the Intelligence to present day London, where it used the Underground system as part of its plan to create a new, isolated bridgehead.
This story was The Web of Fear.
In the early days of fandom, monsters were ranked - by appearances rather than popularity, though there was an element of that as well. The first Target Doctor Who Monster Book was laid out: Daleks, Cybermen, Ice Warriors, Yeti, then Autons and Sontarans - the latter three having featured twice in the series, but the Yeti were first to achieve that. (Of course this was published before the Sontarans made their third appearance in Season 15).
When it came to bringing back the old monsters in the revived series, a lot of people hoped to see the Yeti / Intelligence revisited. It took until Christmas 2012 to do it - and then only the Great Intelligence made it back into the series.
You might have thought that a monster with "Snowmen" in their title might have been an obvious choice for a festive special - and Steven Moffat did bemoan the fact that there were no Xmas traditions left to subvert, in a Doctor Who sense - but the writer opted to go with actual Snowmen.
Men, made with snow.
The original Yeti had been a problematic costume - many children finding them cuddly rather than scary.
This is why director Douglas Camfield redesigned them with sleeker bodies, glowing eyes and guns, and transplanted them into the darkness of the Tube.
This was probably what was at the back of Moffat's mind in deciding not to resurrect them.
By making this a prequel to the first Great Intelligence story - set supposedly circa 1935 - there was no reason to have the big shaggy creatures anyway. The Yeti robots were created specifically to scare people away from Tibet.
The Snowmen is set in Victorian England, so why would the GI make Yeti?
Whenever it snows, everyone - young and old - makes a snowman. They are very easy to create - balls of snow, placed one on top of the other (three spheres if you're American, just the two if British). A carrot for a nose and small stones or bits of coal to make the eyes and mouth. Sticks for arms, and perhaps a real hat and scarf.
The first written record of a snowman hails (no pun intended) from the Netherlands in 1380. He might be better known as one of the greatest genii of the Renaissance, but Michelangelo was also asked to create one for the Medici in 1494.
In 1511 the city fathers of Brussels launched a snowman contest, to distract the populace from a winter food shortage. They were not best pleased when everyone made pornographic snow sculptures.
Don't say you never learn things on this blog.
With The Snowmen, as an alternative to Yeti, Moffat gave us scary looking title monsters - with Hallowe'en pumpkin-style evil-looking features.
The episode instead concentrates on the Great Intelligence, and it uses snow as a physical medium with which to give it corporeal substance. This can fashion itself into the Snowmen, the first of which latches psychically onto a lonely little boy. He grows up to be Richard E Grant - an actor who had actually played two different incarnations of the Doctor previously, one of which RTD2 has attempted to canonise recently.
He's the forerunner to Padmasambhava and Sergeant Arnold - the human puppets from the Troughton stories.
Another link back to The Web of Fear is the lunch box which the Doctor uses to smuggle the Memory Worm into the Institute. This is a souvenir of the London Underground and the Doctor gives its date as 1967 - actually the year of the first Yeti story, though production on its sequel fell into that year.
The Doctor is basically giving the Great Intelligence the idea to exploit the Tube as a potential weakness for the city.
The other big thing about this story is the return of Clara. However, like the first appearance in the series of Jenna-Louise Coleman (as was) this is a false start. She's not the person who is going to become his new companion (sort of, it gets complicated) and is a guest character only, who once again gets killed off.
One of the children she looks after is called Digby, which has prompted fandom to think that he grows up to be the absentee owner of the big country house in which last year's Christmas Special was partly set.
Next time: the Doctor and Clara, spooning at the Shard...
