Roots: The concept of Auld Mortality may spring from the tradition of Roman emperors being told upon their Triumph by a slave that they are only mortal. Hannibal's journey over the Alps (with a few historical embellishments) Christmas stories (the story's mentions of the Gallifreyan Othermass - Auld Mortality is an Auld Acquaintance of the Doctor, harking back to the feast of Steven.") Star Trek's holodeck stories - creating artificial realities with entities that become self-aware. Star Trek: TNG - Badger's positronic brain. Mervin Peakes' Gormenghast Trilogy - The Doctor's strange household and his abdication from the responsibilities of Leadership forced on him by his family - Badger is very similar to a character from the Peake novella 'The Boy in the Darkness' that slots in between the first two books. Old Mortality by Sir Walter Scott. Sapphire and Steel (Auld Mortality hiding in every painting of the Presidential Inauguration, sometimes only a shadow) Sophie's World (running away into the infinite possibilities of the imagination and questioning of what is real)
Intertextuality: Quences, Badger and most of the other mythology come straight from Marc Platt's novel 'Lungbarrow'. 'An Exciting Adventure with the Hassites' recalls 'An Exciting Adventure with the Daleks', while 'A Journey to...' recalls 'A Journey to Cathay', the original title to 'Marco Polo'. The Doctor's final line paraphrases William Hartnell's line at the close of 'The Feast of Stephen'. The reference to a foggy night on Barnes Common comes directly from David Whitaker's novelisation of the first Dalek story.
Goofs: If Quences is non-corporeal how is he able to play chequers? [It's voice controlled - more to the point, the Doctor's dialogue suggests Quences recently regenerated?!]
The air was thick with (silent) carrion birds.
Technobabble: The Aurora Temporalis - The Anvils of heaven from which all time springs
Double Entendres: 'You characters always get uppity and start rewriting your own stories!'
'You're not real, none of this is.'
'...Some cheap scientifically fictional romance.'
'Oh please, this literary self indulgence is getting us nowhere!'
Dialogue Triumphs: 'It takes us all, some more finally than others.'
'Just like you to make a fool of the whole Family. Arse over ceremonial tit in front of the Lordships!'
'I'm a ghost, my disposition is permanently chilly.'
'Don't just assume things only go wrong because God didn't do his research.'
Dialogue Disasters: The very French Gaul accent.
'Grandfather - He's controlling you!' - duh!
'I will feed you to the dogs!' 'Only the dogs! Oh dear, oh dear.'
Continuity: WHAT IF...the Doctor and Susan never left Gallifrey?
'Auld Mortality' is a reoccurring dark presence that haunted the presidents of Gallifrey, reminding them that death is never far away. The Auld Mortalities want a president it can completely control.
Few Presidents seem to reach a second term (or even a second regeneration.) once they have outlived their uses. Of former Gallifreyan heads of state, President Cholem died from slipping on the Panopticon steps and splitting his head open. President Rosieh was poisoned by his own food taster. Precept the Second died from a paper-cut at an archivists' supper. No one knows what an Ordinal-General does; possibly it is archaic flimflam like Almina Crest or Able Gread.
There was a fungal coup on Esto, steep rise in the price of soul in Mephisto Regions. Half of the galaxy have fallen to the Thalek Empire [presumably an alternative outcome of the Dalek/Thal war], whose war cry is "Annihilate!"
The Daily Presidential Bulletins come in paper form (and can be ironed.) And there are still door-to-door hawkers and circulars. In this universe a Supreme Council rather than a High one governs Gallifrey. As well Prydron Academy Gallifreyan records can be obtained from the Bureau of Political Advancement, The Temple of Capital Guilds, and the Office of Public Registry. Transmats are in common use.
Auld Mortality made the Doctor into a writer of adventures of a traveller in Time and Space, living in his TARDIS (which the Doctor forgot). Some of the Doctor's adventures include 'A Journey to Ice-Askar, the Winter Star' and 'An Exciting Adventure with the Hassites'. An Auld Mortality over the Doctor's great-granduncle, Ordinal-General Quences (whose Deathday was 13 days after Othermass) who survived by implanting his psyche into the robot Badger's mind.
The Possibility Generator allows one to engage in a virtual reality. Possibilities and Imagination are two relative dimensions. The controls for the generator don't work within it. It doesn't appear to be common on Gallifrey, as Susan isn't familiar with them, and is probably illegal.
Susan has two grandchildren (a girl and a boy) of her own. She is the daughter of the Doctor's daughter. The Doctor's birthday is on Othermass. Othermass celebrations involve giant puppets.
At the end of the story, the Doctor leaves Gallifrey with Susan/without Susan (who stayed to become the next President of Gallifrey).
Untelevised Adventures: After leaving Gallifrey the TARDIS takes on various forms, an old tree stump, an old minaret, a wardrobe, a revolving door, and an ancient black sarcophagus. The Doctor meets Winston Churchill.
Links: 'An Unearthly Child' (I M Foreman, Wanderers in the fourth dimension),'The Keys of Marinus' and 'The Sensorites' (the planet Esto) 'The Myth Makers' (Aeneas and Dido), 'The Daleks' Master Plan' ("And a Merry Othermass to all of you at home too"). 'The Deadly Assassin' (Pandak).
Bottom Line: "So many possibilities"
One gets the impression that this story, populated with so many 'established' aspects of Marc Platt's Who fiction, doesn't ask the above question 'What if the Doctor never left Gallifrey' rather, 'What if the first Doctor was played by Geoffrey Bayldon?' Bayldon makes a great Richard Hurndall as the First Doctor. However Carole Anne Ford makes rather a meal of her returning role as Susan.