Roots: The Shepherds speak in iambic pentameter. Will compares the TARDIS "flight deck" to the d&eacaute;cor of George Pal's film adaptation of The Time Machine. Operation Paperclip. Heinrich Hoffmann's Struwwel Pieter. Kasta mentions Zeus, Leda and Perseus' mother. Hinterberg employs a Nietzchian metaphor: (History toying with the TARDIS like a giantess) Matthew 27:51 (the 'tearing of the veil') James Joyce ("History is nightmare from which I am trying to awake")
Intertextuality: 'Heat Vampires' recalls Olla, a short-lived comic companion of the same species who accompanied the Seventh Doctor in Doctor Who Magazine. Temperons hail from the Audio Visuals audio series.
Goofs: Will gets the TARDIS acronym wrong ("dimensions")
Double Entendres: "I can't help myself - I think I'm going to go further in."
Dialogue Triumphs: "I suppose you were there? " "I will be."
"Coincidences in the universe are like confetti at a wedding"
Classic Seventh Doctor: "There's one thing you need to know about me, Mister Arrowsmith: if I ever seem sure, it's because I'm never as sure as I seem."
"No wonder half the galaxy are looking for you; they're probably forming an orderly queue to punch you on the nose."
"You've not even seen this planet - plucky little mudball that she is."
Continuity: The Klecht are multi-limbed with dark, eyeless sockets. They are renowned across the galaxies as being ruthless and efficient asset strippers. They use organic technology - stretzioni bombs (using Stretzioni energy). The Spivellin are "lords of the galactic Index and Wardens of the Intergalactic Exchange". The planet New Peerlessness is a prison world with no animals (despite birds and insects being heard on the soundtrack).
The Doctor knows Struwwelpieter by heart, but not how he has come to [experiencing them wipes one's mind - or rather, the mind wipes itself]. They are more ancient than he realises. They float above the ground.
Minnos is the farthest island from the Greek mainland (presumably part of the Dodecanese or Ionian groups).
The TARDIS' Star Chamber contains a galaxy from the Tear of Ragged Restoration, near the universal core. The Doctor rescued it when it was under threat by an insatiable intelligent virus. Will passes through a section of rain forest (inhabited by some creature), a 5-dimensional cinema, a freezer section stretching almost to infinity and stocked with vegetarian meals, and a wood-panelled oval room floating on water (a ship?) Cupboards the size of cathedrals, and libraries filled with "impossible" books. Will infers the TARDIS "command deck" is from a "later" version of the TARDIS as seen previously (in Dominion?). The Doctor says his recent upgrades to the TARDIS have made her "positively mercurial".
Will is still on probation, having been embroiled in a few previous misfires in the field, including something in Bangalore, a "beached Temperon in Yarmouth" and a Heat vampire still at large somewhere in Mexico.
Klein has a PhD. Her parents were Mutte and Ralph. Near Klein's workplace (presumably) is The Huntsman Pub, somewhere in Clapham Junction.
The Doctor is afraid that "the man who comes after me won't be strong enough to do what must be done." He deliberately left one of his old sonics in his UNIT lab in the hope that someone clever enough would reverse-engineer it. His current model is an upgrade, and he gives Will a "sonic" tape recorder (hopefully this is a joke).
Links: UNIT: Dominion, Klein asks after Raine ("she's... elsewhere", says the Doctor) The TARDIS Star Chamber may be the same chamber seen in the TV Movie. The Sirens of Time (Temperons - see also Intertextuality) The Doctor mentions the Eye of Orion. Schalk's tracking by the Sontarans presumably leads into Starlight Robbery. The Doctor's "and didn't we have trouble with the prototype" (Remembrance of the Daleks) The Idiot's Lantern (Will asks the Doctor if he has a motorbike in the Ship)
Unrecorded Adventures: The Doctor has encountered Spivellins before (they flee at the sight of his TARDIS). He heard Schulk's name on intergalactic channels he has been monitoring in the TARDIS (he adapted or 'persuaded' the Ship to do this)
Location: London (including Clapham Junction and Lavender Hill where the TARDIS is resting) 27 September 1990; Dusseldorf, May 1945.
The Bottom Line: "You'd really let a Nazi aboard your Ship?"
Bringing Klein back for UNIT: Dominion was a big ask for such a memorable character already boasting a strong trilogy of her own not too long ago. To bring her back once more would already be tempting fate, but to pair her with an underperforming Sylvester McCoy and Will Arrowsmith, a second would-be companion hailed by some as the second coming of Jeremy Fitzoliver seems positively foolhardy, suggesting Big Finish have some very big upsets in store. As it is, Persuasion is no indicator of a grand scheme or plan, yet.