Roots: Greek mythology (Eris, the goddess of discord). Lucie compares Amy and Farl to "Polly Pocket and [Harry Potter's] Hagrid and Farl the Big Friendly Giant after Roald Dahl's The BFG. Top Gun ("I feel the need for speed") Judge Dredd (anti-gravity boarding) Mary Poppins ("the spoonful of sugar") Scooby Doo ("And I would have got away with it-" "-If it wasn't for us meddling kids?")
Intertextuality: The ubiquitous onomatopoeic description for the TARDIS' materialisation sound ("a sort of wheezing, groaning") comes from several of Terrance Dicks' Target novelisations.
Dialogue Disasters: "That was killer awesome Scotty babe!"
Dialogue Triumphs: The Doctor: "I've seen entire species destroyed, civilisations left in ruins. I've witnessed solar systems vanish in the twinkling of an eye - I've seen things that would freeze your blood. So don't threaten me. Don't ever threaten me."
Continuity: There are no rules on Phobos. Lunar Park was originally to be a large complex boasting a hotel and botanical gardens, but construction ceased shortly after the environment dome was completed and the park's owners have claimed squatters' rights on the site. 'Adrenaline sports' featured include ice-spelunking, gravity boarding, bungee jumping, white water rafting and bicycling (the Headhunter spent some time doing this waiting for Lucie and fell, hitting her head).. An opposing field inside the environment dome compensated for the moon's eccentric and varying gravity. The construction robots are twenty-feet tall. The Park's buggies don't have wheels (from the sounds of them they have articulated legs) and hires most of its equipment - the wetsuits featured have their own temperature regulators.
The Phoban creature uses a singularity bridge to cross the wormhole to enter this Universe. It feeds on adrenalized fear - that is, exhilarating fear rather than terror or panic. Pure fear in great enough quantities actually harms it.
Githeans are huge furry humanoids. They are forbidden to marry outside their species, since they have trouble maintaining the purity of their gene pool.
The Headhunter appears to have the ability to anticipate the TARDIS' destinations.
Lucie drinks coffee and has an Auntie Marnie who is quite large. The Doctor still carries a telescope in what sound to be either numerous or very deep pockets [the occasionally-used fan theory that they themselves are dimensionally transcendental may be the easiest explanation here].
Links: The 'fears' the Doctor reveals to the creature begin with "Evil from the Dawn of Time" (The Curse of Fenric)
Future History: Australia and its accent still survive in 2589 (er, 'bonza'...)
Location: Lunar Park, Phobos, 2589
The Bottom Line: "Maybe you're scarier than the monsters?"
Traditional, and palpably Proppian in its inevitable 'descent' of the Doctor to face Eris. Referencing other 'evil from the dawn of time' stories puts Phobos in a similar camp to Fenric and the later Satan Pit, but the opening scenes and deliberate Scooby Doo ending pull this back, as though Robson doesn't quite believe in the threat of this story either. Still, it's not a bad yarn and he developing friendship of the Doctor and Lucie makes the adventure all the more fun, before the Headhunter's assured appearance.