In the New Traveller's Almanac, a few references to Wonderland pop up. Specifically, the details of The Hunting of the Snark are preserved in its entirety and the events of Alice's Adventures in Wonderland. Though in the later's case, it turns Darker and Edgier with Alice dying from her organs being reversed from her second trip to Wonderland and slowly dying of starvation and the trip before that, being missing for months on end when it only felt like an afternoon. And not to mention Alan and Mina's visit to an unearthly being who turns out to be a Mugwump, which Jess Nevins notes, is similar to the Blue Caterpillar. Just what the hell is going on inWonderland?
The Black Dossier
In The Black Dossier, a section written in a pastiche of Shakespeare, we learn that the original 007 was, of all people, Prospero. At first I thought this connection was a bit far fetched. It wasn't until later that I learned a bit about John Dee's career. Moore has Prospero stand in for Dee in the League universe. Dee, best known as an occultist, was also a spymaster for Elizabeth. He corresponded with the Court in secret, signing his name with a special glyph of his own invention: two circles under the top line of an acute angle.◊ And yes, it was this practice that inspired Ian Fleming during the creation of the James Bond character. I'll never doubt Moore's research again. Also, it's widely thought that Shakespeare based Prospero on John Dee, adding another layer to the symbolism.
The teamup of Bond, Night, and Drummond can be seen as somewhat parallels of Murray's original League. Superficially, they resemble Allan, Mina, and Hyde with their dynamic, with Bond as the established British hero, Night as an influential female member of the group, and Drummond as a very Hyde-like brute. Adding to that is Bond and Night's relationship, as well as Drummond's loving defensiveness of Night (albeit in the context of a godfather, rather than an attraction). Going even further, Bond also turns out to be a parallel of Griffin, being a stealthy and murderous rapist who betrayed England to another power when he killed Night's father on behalf of the CIA. And true to form, the Hyde-like Drummond goes after Bond, although, sadly and unlike Griffin, Bond kills Drummond and gets away with his treachery.
The Black Dossier reveals the significance of Dr. No's name- a tip off that there was No Doctor. But one thing Moore didn't point out- in the novel, No is killed by being crushed by a pile of guano, an indicator that the Dr. No story was, in fact, a load of crap.
In 1910, there is a reference to Ice-9, which suggests that the events of Cat's Cradle happened in the League-verse. However, in that novel, a bit of Ice-9 falls into the ocean and destroys the world by freezing the world's oceans, events that are obviously difficult to reconcile with League continuity. Fridge Brilliance hits when you remember that superheroes are also real in this universe, and if they're anywhere near as powerful as they are in their own comics, the oceans freezing over doesn't seem like an insurmountable problem after all—they deal with stuff like that all the time.
Heck, there may be an even simpler answer. Setting the events of the play in 1910 instead of Victoria's crowning, having the Earl of Gurney show up six decades early, Jack the Ripper... the entire set up is hugely anachronistic. Just like the actual Threepenny Opera is!
Crowley, 60's rock, and Harry Potter. All are treated Satanically in Century. This seems an odd move for the left-hand path follower Alan Moore. Until you remember that people still falsely accused these things of being Satanic, and all fiction is true in this continuity.
A lot of readers say that Harry Potter gets a rotten deal in League:Century, that it's totally inconsistent with the character of the books and that Moore Did Not Do the Bloody Research. But then consider that the Antichrist finds out that he's an Unwitting Pawn, that his adventures were manipulated/staged to prevent him from fulfilling his true purpose. And then consider the final HP book, where the hero finds out he's an Unwitting Pawn for Dumbledore who enabled Harry's rule breaking and hijinks so that eventually he would commit a Heroic Sacrifice against Voldemort, and it's virtually the same situation, only taken one step further and submitted to Character Exaggeration.
Likewise, the Moonchild keeps whining about fame and takes anti-depressants. The character in the books is also quite a Wangst-filled teenager with trust issues and realistically, were it not a children's series, and closer to teenage life in the 90s and The Noughties, Harry would take anti-depressants to cope with his life and him lashing out as a school shooter is the logical correlative of students carrying weapons (wands) in a school environment, finding outlet to direct his rage at being betrayed by adults and constantly undergoing Broken Pedestal, which the Prime!Character frequently underwent in the main books.
Nemo Spin off
In an In-universe interview it's revealed that Janni Nemo fought Godzilla with the Nautilus, perhaps this incident inspired the various Gotengo's that appeared in Toho Kaiju movies
While the comment he made to her staying behind in regards to catching Hyde is still sexist, if you think about it, Allan does it for Hyde's protection more than Mina's. He's well aware of the crimes Hyde has committed, especially the murders and rapes. Allan's also aware of Mina's powers. He fears if Mina catches wind of Hyde's crimes she might tear him apart.