A couple human characters make references to John Carpenter’s The Thing when referring to Ghidorah and/or Outpost 32. Funnily enough, the outpost in the movie was based on the same film, with a couple more subtle Shout-Outs.
A somewhat In-Universe one: both the author, and Vivienne In-Universe, are fans of Doom, and there's a recurring reference to Doom Eternal throughout the story.
There's a subtle reference to Dragon's Dogma in Chapter 13, fitting since the dragon Grigori in the game has been described by the author as San's voice.
Chapter 13 features one to Jurassic Park. You'll know it when you see it.
The Nightmare Sequence in Chapter 14 was partly inspired by Silent Hill, and it shows with the setting and the looping.
Chapter 16 features a mental shout-out to A Clockwork Orange by Vivienne, which is made all the more appropriate by how music (or rather Terrible Ticking inside Ghidorah's minds) originally played a role in Ghidorah's own Ax-Crazy.
In Chapter 16, Vivienne borrows a particular nostalgic catchphrase from Doctor Who.
A couple minor characters flippantly reference Foxy from Five Nights at Freddy's, appropriately mirroring the release of the movie during the same Hallowe'en season that this one-shot was published.
One of the floats at the Pensacola Hallowe'en street parade is the "Belmont Street Belmonts", modeled after exactly who they sound like. The author is in fact a Castlevania fan.
Mark — who's dressed up as Jason Voorhees for Hallowe'en — has a joking faux standoff with a block party host who's dressed up as Freddy Krueger.
Whilst the story indicates San's head was indeed forcibly ripped off at Isla de Mara, rather than being shed by Ghidorah like a reptile's tail to try and escape Godzilla (as has been speculated by some King of the Monsters viewers); the author still referenced the theory, by stating it's what Godzilla assumed happened when San's head tore away in his jaws.
In the AbraxasVerse Timeline, the Hollow Earth element is named by the author after the MacGuffin from the aforementioned Xenogears, which is also a primordial Green Rocks found on Earth which humans attempt to replicate and attempt to use to power superpowerful technology, often with catastrophic results. Mechagodzilla makes a direct reference to the actions of a manmade, thinking, mobile and technological weapon of war within that franchise. And Word of God confirms that Kiryu's supercomputer brain is named after a certain piece of Xenogears lore designed for basically similar purposes.
The Fleet being sense freaks who horrifically mutilate themselves for the sakes of feeling sensation is a reference to the followers of the Chaos God Slaaneshi in the Warhammer franchise.
While the characterization of the Fleet's master, the AbraxasVerse incarnation of Gigan, is based by the author (1, 2) on Albedo's characterization in Xenosaga: as a sense-obsessed, exceptionally depraved and cackling sadomasochist who is obsessed with sensations.
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