Book:I Shall Wear Midnight/Annotations
(Doubleday hardback pp11-13) The scouring fair and the Giant: this still happens in England, where a remarkably similar and somewhat priapic giant is carved in the chalk at Cerne Abbas, in Dorset. Every so often his lines need cleaning. Apparently for many years postcards of the giant were the only pornographic images that could legally be sent through HM Royal Mail. Meanwhile at Uffington the White Horse is similarly (though less ribaldly) scoured, and the event is celebrated by a fair, with all the usual entertainments, including Cheese Rolling and ducking for apples, though not apparently ducking for frogs.
(Doubleday hardback p 103) Still, it could have been worse, she told herself. There could have been snakes on the broomstick. Terry is fond of this urban myth. See the relevant annotations for The Fifth Elephant (hypothetical snakes on a sleigh) and Carpe Jugulum (putative snakes in a coach). This one could very definitely also be an allusion to the film Snakes on a Plane...
(Doubleday hardback p 105) Tiffany's landing of a stricken broomstick on top of a moving coach almost exactly mirrors the standard operating procedure for aircraft landing on the deck of a moving carrier at sea - all that's needed now is the arrester hook and transverse cable. Another first for research witchcraft, after ravens used as black-box flight recorders, and in-flight refuelling?
(Doubleday hardback p 118)
Because you're worthless - a play on the commercial slogan for cosmetic company Loreal. ("Because you're worth it")
- for the hag in a hurry.
(Doubleday hardback p 137)
"I told you to find him; I didn't tell you you were supposed to pull the doors off!"
Tiffany's rebuke to the Feegle echoes the famous line in the movie, the Italian Job. See also annotation to The Fifth Elephant, Corgi paperback edition p307.
(Doubleday hardback pp 149) Long-term solitary confinement prisoners, often dangerous killers, keeping caged birds for company in their cells - think The Birdman of Alcatraz, now a prison cliche. There is an annotation for another Discworld book that covers similar ground? This also resonates with "it's a sin to kill a mockingbird," the only thing called a sin in the Harper Lee novel of the same name.
Depressingly, the real-life "Birdman of Alcatraz" never kept caged birds in his life, and certainly not during his incarceration. Robert Stroud was a devious, manipulative and thoroughly loathsome double murderer with paedophilic tendencies, who knew how to play a good PR game. He convinced a charismatic lawyer to fight his appeals. This led to a romantic and wildly inaccurate book being written about him which was later filmed by Hollywood with Burt Lancaster in the title role, which established the fiction firmly in the public eye. (Source: Perfect Victims by Bill James, Simon and Schuster, 2011)
(Doubleday hardback p 164) Wee Mad Arthur gloomily intones "It will be certain death to go in there. Certain death! you'll all be doomed!" This was the catch-phrase of Scottish comic actor John Laurie, who played the gloomy undertaker and over-age soldier Private Frazer in "Dad's Army" Share the doom here (page ref needed).
(Doubleday hardback pp 176-177)
Since last being heard of in Equal Rites, Simon is described (via third-party accounts) as having let his illnesses and allergies multiply to the point where he has become Unseen University's analogue of Stephen Hawking - speaking to peers through a machine (HEX?) and unable to move, talk, or do very much for himself. Some of this is related via Esk, who can be described as a reliable witness.
..."the young Eskarina had met at the University a young man called Simon who had been cursed by the Gods with almost every possible ailment that mankind was prone to.
But because the Gods have a sense of humour, although it's a rather strange one, they had granted him the power to understand....well, everything. He could barely walk without assistance but was so brilliant that he managed to keep the whole universe in his head. Wizards... would flock to hear him talk about space and time and magic as if they were all part of the same thing. And young Eskarina had fed him and cleaned him and helped him get about and learned from him - well, everything." (I Shall Wear Midnight. pp176-177)
And Simon describes part of the knowledge as elasticated string theory, a phenomena which Eskarina says, in a discourse with Tiffany, has at least sixteen different dimensions... compare this to Hawking on superspace and string theory.
Interestingly enough, on page 332, we learn that Eskarina has a son, whom she must protect. This is the only mention of him in the book. Theories about this tantalising standalone fact may be found on the Discussion page of the Eskarina Smith entry (here).
(Doubleday hardback p 175)
When Mrs Proust performs magic on the statue of Lord Albert Rust to turn it into a temporary Golem under her will - think of the song "The Equestrian Statue" by prankster musicians the Bonzo-Dog Doodah Band, in which a statue in the park takes it into its head to wake up and have a canter up and down the square. ("Little old ladies stop and say "Well, I declare!"). Listen here  .
(Doubleday hardback pp 216) Rob Anybody describes the abortive attempt to evict the Feegle as having been carried out by a bunch of "mound-digging Cromwells".
This is a strange expression for the Disc, as Oliver Cromwell was the Lord Protector of England who is even today vilified for a policy of mass slaughter and destruction during his campaign in Ireland. Fan-fiction aside, there is no "official" Discworld analogue for Ireland or all things Irish*, and the only other analogue to Cromwell in the writings is Stoneface Vimes - a man who, while capable of executing a King, would not have countenanced the destruction of a city and the slaughter of all its inhabitants. A Vimes would happily kill a King, but protect and serve the people.
Perhaps on their journeys through the dimensions, the Feegle may have visited Ireland in the 1650's and 1660's; Irish folklore preserves the myth of a terrible, wrathful and cunning Little People living in mounds and barrows, who are to leprechauns what Feegle are to flower fairies. Little People are, after all, common to all the Celtic mythologies - Scottish, Welsh, Manx, Breton and Irish.
(*The otherwise unknown and unreferenced country of Hergen has been proposed, but this is strictly non-canon, with nothing to support it, except its geographical location on the far side of Llamedos)
it is interesting in this context that Unseen Academicals introduces a place on the Disc with the very unambiguously Irish-sounding name of Cladh. There may well be a Discworld Ireland which is yet to be revealed?
(Doubleday hardback p 199-200) The goings-on at the castle in the run up to a funeral and a wedding. Why is this reminiscent of Swamp Castle in Monty Python and the Holy Grail? Especially when a seemingly dim guard (Preston) is not quite getting it right about the need to lock up a prisoner, and an increasingly exasperated employer cannot get the idea across...
(Doubleday hardback p 274) The world needs cheesemakers. Not a million miles away from Blessed are the cheese-makers, a line from Monty Python's Life of Brian.
(Doubleday hardback p 316)
...by the pricking of my thumbs, something wicked this way comes.
Shakespeare again: Macbeth. Alluding to the ability of a witch to sense things others cannot. See also the line early in Wyrd Sisters (page?) - "Can you tell by the pricking of your thumbs?" "By the pricking of my ears."
[Somebody please add a Doubleday page number] The strength of the witch is the coven and the strength of the coven is the witch" seems equivalent to Kipling's "Jungle Law" "The strength of the wolf is the pack and the strength of the pack is the wolf"