Classical Mythology/WMG

The Titans actually represent another pantheon worshipped before the Olympians
They weren't even demonised, since Chronos was appearently benevolent enough to lord over a "golden age". They simply were were buried by newer traditions, so mythology took that to a literal level.

Apollo and Dionysus are the same person.
This is actually less a WMG than a potential bit of theology that is invoked by some Classical writers (I don't remember who all, could link later). We have two gods who are both gods of destruction (literally in the case of Apollo [Apollwn works best, I think, from Apollumi, "I destroy," given how vengeful and related to "acts of God" his cult is; more figuratively in Dionysus, who destroys as in removes structure) who occupy Delphi and grant prophecies (Dionysus occupies it during the winter months, or so the story goes). As such, both share a prophet/seemingly submissive role with a fertility goddess (Gaia in both instances; Dionysus occasionally when associated with Demeter/Cybele/etc.). Both are renowned for their good looks (Dionysus is a Bishounen while Apollo is the god of beauty) and are patrons of gays (Dionysus is specifically listed as the patron of what is the Greek equivalent of BLGT matters and would be the patron of such modern things as Mardi Gras; Apollo's most memorable loves are those with his [usually doomed] male lovers). Both have a thing against Thebes (Dionysus: Pentheus as Apollo: Oedipus, but then again everything happens in Thebes). Both are associated with retinues of musical women (Maenads and nymphs, and Muses and other nymphs)...the list goes on, from how the origin myths make the two foreign gods (Dionysus is the alien god who has been with the Greeks since the Minoan era, while Apollo is the native god with contradictory paths of origin and no record in Linear B) to various symbols (snakes, musical instruments) and an association with youth.
 * It's a Jekyll and Hyde arrangement. Dionysus is the god of the wild creative highs that require completely forgetting yourself and setting about to a frenzy of expression; Apollo is the god who helps you out when you realize its faults and carefully craft it into a measured and more perfect art. In other words, when Apollo gets drunk, he turns into Dionysus.
 * Then this really changes the dynamics of character duos based on the two, like Enjolras and Grantaire from Les Misérables

Aphrodite is a time-traveler.
She wasn't born rising out of the foam; that's just the earliest time in history where she exists. At some point in her personal timeline after she's fully grown and incredibly beautiful, she gets her memory erased and is sent back in time to her "birth".
 * Hephaestus also was a time traveler, or more correctly, he created a time machine that sent Aphrodite to the past (accident or not, is another WMG), himself time-travelled as well and helped to give birth to Athena in this form.
 * Alternatively, Aphrodite is a Time Lady and the seafoam is her TARDIS.

Athena would one day overthrow Zeus
The prophecy just stated that the child of Zeus and Metis would overthrow Zeus. Everyone just assumed this would only apply if it were a guy; because of cultural perceptions. A woman be the King of the Gods? As if.
 * She also one-ups Zeus in that even though he ate her the same way Uranus( Um hello here? Uranas is Zeus' GRANDFATHER..not his FATHER Kronos is Zeus's father) ate him and his brethren; she busts out of his body anyways.
 * Actually, that is not true. Zeus was never swallowed by his father, and his brothers were swallowed by Cronus. Metis was already pregnant with Athena, but was swallowed before Athena was born, so Athena was born in Zeus, not swallowed by him.
 * Considering the fact Gaia already had a grudge against all generations of gods and each time used someone to kill the ruler she didn't like (she gave birth to Kronos to castrate Ouranos and raised Zeus against his father), its not much of a stretch she motivated Athena to end with Zeus rule. This time, Gaia would probably be satisfied, as Athena seems fair compared to her precursors. Its just a matter of which gods will be killed and which ones will join her.
 * Hold on though; You literally CAN'T have a female chief deity on Olympus. What would her successor chop off?
 * Her breasts, of course.
 * Or her vagina.
 * The vagina is an internal structure and can't be "cut off." The closest fitting structure on the outside would probably be the clitoris.
 * You could carve around it, maybe...
 * Athena didn't have a Successor. That's why we don't see Greek gods any-morrr... God is a woman. You Can Panic Now.
 * So it appears Kevin Smith was right...
 * And considering the Greek opinion on fighting fate...

Hephaestus is somehow related to the Cyclopes
Both: Both seem to serve the same purpose in Greek Mythology: ugly, deformed, brilliant craftsmen hired by the gods to create things.
 * brilliant craftsmen and smiths who are good with their hands.
 * have a paternal figure in Poseidon.
 * have contradictory origins that could be explained via time travel.
 * ugly but skilled.
 * survive things that should have killed them via repair. The Cyclopes were killed by Apollo for creating the lighting bolt that killed Phaeton, but were later stitched back together; Hephaestus was defenestrated, but made himself robot legs.
 * credited with the creation of one or more golden apples, the pantheon, and Zeus's lightning bolts.
 * possess severe handicaps. Cyclopes have one eye, Hephaestus has no legs.
 * lack a motherly character in their life.
 * seem to only have one parent.
 * are male.
 * Maybe Hera had him in an affair?

OK, someone Did Not Do the Research: The cyclopes are Hephaestus' great uncles.

Athena was a wholesome crossdresser
Going to above theory, Athena was actually a man, and knew that the best way to survive was to pretend that he wasn't the son that would overthrow Zeus.
 * Imagine Hephaestus' surprise.
 * Why would Hephaestus be surprised, or even ever find out? Unless he was fitting him for armour or something, he'd never have a reason to find out. If you thought they were married, that's wrong. Hephaestus is married to Aphrodite, and that's referenced on this very page.
 * Some myths involve Hephaestus attempting to rape Athena, but her managing to evade him. Unless Hephaestus is as undescriminating as the rest of the gods, realizing that the woman he's attempting to rape is actually a man would be quite a surprise.

Hephaestus is an early Spark, possibly a Heterodyne
It fits in with his general characterization. Hephaestus's robots could have been clanks, and his assistants and/or the Cyclopes could have been constructs.

Hades really is planning to take over Zeus's throne, but for benevolent reasons.
The God of the Underworld, being much more decent than the rest of the gods, is disgusted by their Jerkass tendencies and hates them all. He became ruler of the Underworld as part of a Xanatos Gambit to both get some time away from the rest of the gods, and to have a good secret base to plan in secrecy.(His Helm of Darkness is handy too.)

Building on this interpretation, Hades generally leaves man alone because he wants to avoid bad publicity with them, so one day when they get tired of the rest of the Jerkass Gods of the pantheon, Hades will suddenly be much more beloved and be in a good position to take over. He's building an army in the Underworld in secret from all the souls of the dead who come into his domain, hence why he is so harsh on anyone who dares try to cheat death or bring someone Back From the Dead, thus depriving him of new recruits. He kidnapped Persephone in order to have an accomplice with which to plan, and a way of ensuring her mother Demeter's loyalty when the time comes to actually move against their brother, which is why he is so protective of her; in addition to being his wife, she also knows a lot of crucial information about his scheme and is too valuable in influencing Demeter to lose.

However, one of the other gods(or perhaps a mortal) found out about the plan, but wasn't believed by the other gods. So, they launched a campaign of Malicious Slander in an attempt to make Hades look like a God of Evil, which is why Everybody Hates Hades. However, the backlash against this slander will cause the intelligent fans of Classical Mythology to try to improve Hades's reputation. Phase one is his positive portrayal in The Percy Jackson Books. All of the above is part of Hades's plan.
 * So Hades is really Odin, and Valhalla is where he's training his ghost army, and the Olympians are the Jotuns?

Tartarus was a Lovable Traitor
One of the lesser known facts about Tartarus was that in addition to being the closest thing the greeks had to Hell, he was also a diety like Gaia(and shacked up with her a few times, as well). He was also the go-to guy for the head god whenever they needed to imprison someone or something, first Uranus, then Cronos, then Zeus all had enemies to lock up in Tartarus. There's no record of Tartarus ever rebelling or fighting against the most recent usurpers, where-as Gaia rebelled against the reigns of each of them, and the fact that Tartarus was powerful enough to hold each of the beings that were imprisioned within him suggests that he probably could have put up a fight if he wanted to. None of the new God-Kings ever start to question Tartarus' loyalty, either; they all just seem to accept that he'll willingly act as a jailor for them. Anyway, end result of this theory; Tartarus is mentioned a few times in the New Testament, interchangably with Hell, which suggests to me that Tartarus was simply a go with the flow type of guy who was perhaps biding his time, surviving the downfall of the greek pantheon by being adopted into Christian lore as Hell.

The Greek gods screwed themselves over,leading the the Judeo-Christian God.
Considering what they've done, the Greeks must've been pissed deep down. Eventually they overstepped their line, leading to a Kratos-like figure that organised a rebellion via Xanatos Gambit. The gods were too arrogant too consider this, allowing several instances of Like a Badass Out of Hell, topping it off with a massive civil war between the gods that led to their defeat, with only Athena and Hades remaining. With little competion, the Abrahamic God took over, and the rest is history.
 * Funnily enough, this is actually considered to be one of the reasons that Christianity eventually became so popular in Europe: the Greeks and Romans were tired of what they perceived as their gods' antics and weren't spiritually fulfilled.
 * So this is semi-confirmed?
 * Except that plenty of pagans did NOT willingly convert to Christianity, and the Christian emperors outlawed non-Christian religions (and non-Catholic denominations), persecuted everyone who wasn't Catholic, ordered the destruction or vandalism of non-Christian temples (and non-Catholic Gospels), and actively went out of their way to persecute the other religions into extinction. Even so, it took until the 20th century before the last secret adherents to the Etruscan religion were stamped out (an Anthropologist of the 19th century actually encountered them and documented their practices and myths), and the other pagan religions probably also lasted for a while underground. The idea that pagan religions died because they were inferior and doomed and the pagans never actually liked them is 1500 years of Christian propaganda, as is the myth that Catholicism was the only denomination before the Protestant Reformation.

Hephaestus was destined to overthrow his father.
Something of the Spear Counterpart to the Athena WMG. The prophecy that Prometheus was said to know, concerning Zeus's fall from grace in the future? That history would repeat itself: Zeus's last "true" heir (i.e. a child born within his wedlock) would devise the means to destroy him, and take his place on the throne. Chronologically, Hephaestus- lame, blind, arguably hideous, industrious, and technologically ingenious- is Zeus's and Hera's last son. Hera locked her ugly little son in a volcano out of disgust, but Zeus enforced this because of the prophecy.
 * Minor thing, but I heard it that Hera is actually very fond of Hephaestus, and Zeus threw him out of Olympus in the middle of a temper tantrum.
 * In some versions of the story of Hephaestus's birth, Hera conceived him on her own out of jealousy of Zeus's birthing of Athena without a female, with the implication that he's the only imperfect god because he doesn't have a father. But, obviously, this is Depending on the Writer.

The stone that Cronus ate so long ago has some deep connection with Zeus.
Besides it being an Omphalos stone (used to denote the "navel" of the world), why else would the oracle at Delphi had found it and saved it?
 * The fact that it sat in the stomach of the Titan King for quite some time would have to give it some powers. Dionysus gained divinity by simply being half-god and finishing up his gestation in Zeus' leg.

Hepheastus isn't actually ugly.
In fact, he may even be a bit handsome. Why do they say he's ugly? The gods' true forms are the absolute perfection of human physique, while Hepheastus looks more like us. By their standards, he's hideous(even more so, since they expect their own kind to have stunning beauty.) Beauty is in the eye of the beholder, after all...

Heracles had stomach cancer.
In the Roman version of the 12 Labors myth, Hercules was attacked by a crab that distracted him from his tasks. Under the premise of the guess, the Romans heard "Heracles' task was made difficult by a bout with cancer" and thought that "Giant Enemy Crab" was a better translation than "stomach pains".
 * FYI, the Latin word for crab is cancer.
 * Aye, based from the Greek for crab which was used to describe cancers. Thanks for bringing that up, in case someone happened to not know the etymology.

Tartarus was a Lovable Traitor
One of the lesser known facts about Tartarus was that in addition to being the closest thing the greeks had to Hell, he was also a diety like Gaia(and shacked up with her a few times, as well). He was also the go-to guy for the head god whenever they needed to imprison someone or something, first Uranus, then Cronos, then Zeus all had enemies to lock up in Tartarus. There's no record of Tartarus ever rebelling or fighting against the most recent usurpers, where-as Gaia rebelled against the reigns of each of them, and the fact that Tartarus was powerful enough to hold each of the beings that were imprisioned within him suggests that he probably could have put up a fight if he wanted to. None of the new God-Kings ever start to question Tartarus' loyalty, either; they all just seem to accept that he'll willingly act as a jailor for them. Anyway, end result of this theory; Tartarus is mentioned a few times in the New Testament, interchangably with Hell, which suggests to me that Tartarus was simply a go with the flow type of guy who was perhaps biding his time, surviving the downfall of the greek pantheon by being adopted into Christian lore as Hell.

Hera founded the Amazons.
What better way to show up her adulterous husband and the other male deities than to create a society in total contray to the sexism and misogny of the time?
 * Except for the fact that Ares (A male god) was the father of the Amazons. Perhaps it was a joint venture between the two to get back at Zeus?
 * More likely, Ares sired a bunch of Amazons, then forgot about them, then Hera forged them into the Badass Army of misandrists we all know and love.
 * If that was Hera's plan, than it backfired pretty thoroughly, given that the Greeks used the Amazons as an example of why women shouldn't be allowed any power. "Look how evil and crazy the Amazons are? Women obviously can't rule! Let's not let that happen!"

Athena has some connection to hive insects, ants in particular
Firstly, there's her origin story. Her mother was turned into an ant and eaten by Zeus to stop her from giving birth, but Athena was born anyway, and burst out of Zeus's head. Secondly, Athena is sometimes viewed as a symbol of feminism, second only to Artemis, and most hives are ruled by a QUEEN. She is also the goddess of wisdom and battle, and hive insects are notoriously well coordinated. Finally, there's the famous myth about her and Arachnea, where she got jealous of her weaving skills and turned Arachnea into the first spider. Now think about it, what kind of animal preys on insects like the ant? Is it possible Arachnea's children are trying to take revenge?