[[WMG: Nut and Geb are aspects of Gaia and Ouranos from Heroes of Olympus]]
They have very different personalities, just as Aries may be a BloodKnight Jerkass while Mars is a [[ReasonableAuthorityFigure reasonable]] SergeantBadass. But they both have Earth and Sky being held apart by another power. Given the events of Heroes of Olympus this may have made taking a message between them a case of NiceJobBreakingItHero, but it also may give some hope: if they can arrange for the Geb aspect to supplant Gaia, mother earth won't be evil anymore. That would fit better with the ecological message from the previous series.

[[WMG: The Faust family is descended from ''the'' {{Faust}}.]]
The universe of this series fits AllMythsAreTrue and at least some elements of the Abrahamic religions are shown to be true (Moses defeated the magicians of the House of Life). So it's possible that Mephistopheles exists in the story's universe as well.

[[WMG: In-universe Creator/LaurenFaust is a wizard.]]
She is a wizard, but never used any ancient knowledge on her works beyond the point of reference, all her doings such as the creation of WesternAnimation/MyLittlePonyFriendshipIsMagic are pure skill.

[[WMG: Related to above, in-universe brony comunity is partially aware of Creator/LaurenFaust being a wizard.]]
This is treated mostly as a meme by the comunity and no one actually takes it serious, however, the few bronies who too are wizards have a deep respect for her.

[[WMG: The books' titles relate to their endings.]]
* The Red Pyramid has Set on the loose with Apophis on the rise, while The Throne of Fire ends with a weak Ra and a preparing-to-escape Apophis, and soon there'll be The Serpent's Shadow.
* Now, in Egypt red is a color of chaos while black is a color of order. So the first two books with their cliffhanger endings have titles that evoke that color (Red is red, and fire is usually depicted as red) while the third one evokes the color black (shadow- black). This hints at an orderly, happy ending to the trilogy.

[[WMG: There will be a three-way crossover with ''Literature/TheKaneChronicles'', the Percy Jackson series, and Rick Riordan's future series based on Norse mythology.]]
* They're all in the same universe, and it's implied that it will happen at the end of The Serpent's Shadow. Plus, it would be [[CrazyAwesome awesome]].
* Further WMG: other mythologies will also appear, although not to the same degree.
* As of the short story "The Son of Sobek" Percy and Carter have actually met, and Percy now has a hieroglyph on his hand that will summon Carter if a need arises. Carter is dreading that day.

[[WMG: The Egyptian God of Ice will be discovered in the above-mentioned MassiveMultiplayerCrossover.]]
* Either that or Felix will figure out a way to channel one of the other pantheon's gods, possibly the Norse, since those gods are the only known pantheon to have an Ice Deity.
** He'll be the first magician to follow the path of Skadi.

[[WMG: The recordings themselves will play a role in the crossover.]]
The second book makes it quite clear that the Kane Chronicles are being published in-universe. While the LiteraryAgentHypothesis is nothing new, it would be a good way to unite the two casts, so at least one of the demigods will have read them. Nico's a likely candidate - he's nerdy enough, and he'd certainly be interested in Egyptian mythology.
* And Creator/RickRiordan himself will appear as a character, along the lines of Creator/CliveCussler showing up in some of his novels.

[[WMG: Felix will be the main character of a SequelSeries]]
* It's implied several times that he's exceptionally powerful but he never really gets a chance to show what he can do. In a sequel, not necessarily the crossover, he could be the one with the power and wit to hunt down Setne.
** Or, according to a Headscratcher theory about Riordan making a Norse series, Felix could be channeling a Norse god, Since Egypt doesn't HAVE an ice deity while the Norse do: Skadi.

[[WMG: Felix will take over the Antarctic Nome]]
And given access to all that ice and all those penguins, he will ''become'' the Egyptian god of ice and snow.

[[WMG: Felix is channeling Khione from ''Literature/TheHeroesOfOlympus'']]
* That's why Khione has become so much more powerful and active in the world recently: she now has a mortal avatar binding her to the world.

[[WMG: Felix is a demigod]]
He doesn't know he's a demigod, and when he found the Kanes, everyone assumed that he was a normal magician. Reasoning: In ''The Crown of Pltolemy'', Percy sees through Nekhbet's eyes and learns that a strong, ultraviolet aura is the mark of a greek demigod. In ''The Serpents Shadow'' Sadie says that Felix has a powerful purple aura.
Possibly, she's seeing the color ultraviolet but is unable to recognize it, or her previous status as an Avatar lets her brain automatically translate ultra-violet into regular violet when seeing the color set in a magical context. Alternatively, demigods simply have a regular purple aura that doesn't become ultra-violet until they reach some major milestone, such as being claimed, learning what they are, etc.
* Well, purple is the color of royalty so Ultraviolet would signify super-royalty by aura-vision logic. Maybe how purple you are says how powerful a demigod you are.

[[WMG: Alternately, Felix is a legacy]]
Legacies are the children of demigods. The more generations between them and their godly ancestors, the less powerful they are, like Octavian being a legacy of Apollo but not having any divine gift from him. But if a demigod/legacy fell in love with someone with the blood of the pharaohs, then their child might be a magician with an affinity for a power related to their godly ancestor, even if there is no Egyptian aspect of that god. Felix is probably descended from either Khione, the Greco-Roman godless of snow or, even more likely, Skadi, Norse God of ice (we don't know if the Norse group can have legacies, but we have no reason to believe they can't) a Felix being descended from a Norse God would tie The Kane Chronicles to Literature/MagnusChaseAndTheGodsOfAsgard, letting them in on the crossover action. Felix being a legacy would also explain why his aura is just purple, rather than ultraviolet like other demigods, he's got a weaker connection to his godly ancestor.

[[WMG: Sadie Kane is in the same world as Polly Shulman's The Grimm Legacy]]
* Sadie Kane is the name of a minor character at Elizabeth's high school
* Sadie Kane and The New York Circulating Repository are both in New York. In the same kind of area
* The implications - Riordan's demigods and magicians live in a world and practically right next door to a library that houses pretty much any fairy tale or science fiction artifact - most of which are fully functioning and able to be checked out. I shudder to think of the mischief they could get into. Does Magnus hang out at this library when he's homeless?