I might be wrong here, but I noticed that the other camp was forbidden for Chiron (and likely Lupa) to have mentioned. If I recall correctly, Chiron never actually mentioned that camp at all and let the characters figure it out themselves.
Percy's absolutely furious that he lost so many months of his life. Of course, anyone would be, but when you take demigod lifespans into consideration...
Most Roman demigods don't seem to be dyslexic, and in fact it doesn't really make much sense that a lot of them would be, given how close Latin is to the Romance languages. Latin and the modern Romance languages all use the same alphabet, even, so it makes no sense that they would be dyslexic. Instead, since the Roman numeric system is completely different from the Arabic one in modern use... they're clearly all dyscalculic!
Turns into a case of Fridge Logic, when yes, Frank does state that Roman demigods are dyslexic in Son of Neptune. He claims to be more of a freak because he's a spelling champion among dyslexic demigods. Apparently, dyslexia also applies to reading math problems, so it could be that.
Jason Grace sounds like a huge case of Remember the New Guy. Surely, you'd think that if Thalia had a brother, she'd have told Annabeth and Luke, right? Well... she probably had such a mental breakdown she blocked it out and assumed that Jason was dead. When she met Jason in The Lost Hero, she had more time to adjust.
So nearly all of the known Seven have special powers respective to their godly parent. Piper has charmspeak and looks good no matter what, Leo has pyrokinesis, Hazel has geokinesis and can control precious minerals, Frank can shapeshift and apparently is a tactician. Percy and Jason are the sons of Poseidon and Jupiter (big important gods) respectively and are simply put, the Heroes. Capital H. I honestly thought that in general, they where all very Mary Sue/Marty Stu-esque. Except Percy, who got character development in the last series. But then I realized that of course they are going to be that way, they were chosen by the gods themselves. The gods aren't going to just pick some random normals! They are going to go for the gold! The very best! The cream of the crop!
Yeah since their enemy is Gaea, the freaking PLANET itself(or at least its personification), the Gods themselves say she can't be defeated only put to sleep, so of course they are going to pull all the aces in their sleeves, its an "all-or-nothing give it everything you got" scenario
Unlike most demigods, Jason doesn't seem to have dyslexia. Why? He's a Roman demigod, and their minds are wired for Latin, not Ancient Greek.
Another Fridge Brilliance moment happens because Jason wasn't directly claimed when he went to the Greek Camp Half Blood. he was already claimed over at the Roman camp half blood, and it was Hera who sent him over there.
The Cold War is referred to as a war between the East and West (Greek and Roman) demigods. This may sound strange until you realize that Roman influence moved East, and then North, into Russia. Moscow has also been called the Third Rome.
Where was that mentioned? Chiron said that most civil wars were covers for wars between the Greek and Roman demigods, but the Cold War wasn't a civil war.
Aphrodite is the goddess of love, lust, and beauty. Of course her children look like Mary Sues!
Why do they wear purple shirts at the Roman camp? Because purple was a symbol of power in Ancient Rome.
Thanatos's part in SoN. In a myth, Sisyphus chained Thanatos up but was freed by Ares (who was getting bored because what fun is war without dead people?). In the series, Frank, son of Ares/Mars, frees him (at nearly the cost of his stick of life, which by itself is a parallel to Meleager).
Having demigod children of different ethnicities (something only mildly touched upon in the first series), without any trace of Greek in them, may seem odd at first—- until you remember that the gods don't have DNA. In that case, of course their children would take from their mortal parent!
Percy is explicitly stated to have his fathers dark hair and green eyes and Annabeth has her mothers grey eyes.
It's also mentioned that the god's "don't really have DNA" which is generally why people are a bit more relaxed about dating in camp, since pretty much all the gods are related.
I wondered if Rick Riordan was going to address the fact that, regardless of who the 7th halfblood is, the numbers would slightly favor one camp or the other (either 4 Greek demigods or 4 Roman demigods). Then I realized the issue was solved with Frank, who, while a son of the Roman Mars, is also a descendant of the Greek god Poseidon; he could, technically, count for both camps, making the numbers even.
That just makes the tallies 4 Greek (Percy, Annabeth, Piper, Leo), 2 Roman (Jason, Hazel), and Frank.
Unless you also take into account that Aphrodite told Piper that she would be the mediator between the two groups. Using that, it becomes 3 Greek (Percy, Annabeth and Leo), 2 Roman (Jason and Hazel) and Piper and Frank on the sidelines. Makes it a bit more balanced, not much more, but still.
Jason is torn between Reyna, a daughter of Bellona, and Piper, a daughter of Aphrodite. And what are love and war but the peaks of human emotion?
It also brings to mind the saying "All's fair in love and war."
Back in The Last Olympian, when Percy bathed in the River Styx he used his memories of Annabeth to act as his anchor to the world. His love for her is magically hard-coded into him now, so no wonder Hera couldn't completely banish those memories.
Nico's crush on Percy makes sense when you think about how he was 12 at the time and 14 now, around the time that a person would be discovering their feelings.
That and the fact that there's never been a chapter told from Nico's point of view. In fact, all of the first series (when the whole affair started) and many chapters in The Heroes of Olympus are told from Percy's point of view, who at the time thought that Nico had a crush on Annabeth.
Bob's ability to inspire Damasen to try to change his fate makes a lot of sense when you realize that Iapetus was The Lord of Mortality and one of the cruelest and most evil of the Titans. Bob's ability to rise above that showed Damasen that change for the better, be it in a being or in one's destiny, is not unattainable.
The scene in Split where Favonius tells Jason and Nico of his crush on Hyacinthus seems a bit unnecessary, but once Nico's crush on Percy is revealed, it seems that Favonius might have been trying to discreetly protect Nico, by judging Jason's reaction to his own sexuality.
Calypso is angry at the gods for neglecting to lift her curse. Yet who is the very next hero she meets? Leo, who has no love back in the world to forsake her for and possesses the skill to break Ogygia's isolation.
Nico telling Percy about his crush nonchalantly seems to imply that he is over him. This may seem out of nowhere, except the only thing that implied he still loved Percy was Jason's POV. All Nico said was that he used to love Percy. When we finally get Nico's POV, he offhandedly makes jokes about his crush on Percy several chapters before he actually tells him, which are bitter but still light-hearted. He's been over Percy for a while, even if the memory is painful.
In House of Hades, Nico's attitude towards his crush on Percy, avoiding everyone because he believes he won't be accepted and going so far as to say he hates Percy, is absolutely heartwrenching in the face of his past. Considering that before his mother moved him and Bianca to America he spent his formative childhood years growing up in fascist catholic Italy during the holocaust, with gay people being interned just as much as jews and the global attitude towards non-heterosexuality being absolutely poisonous, it's no wonder he's so scared to admit it. Jason's right; Nico admitting it is the bravest act that any character in the series has ever performed.
Fridge Tearjerker: Nico would also know that Hazel grew up in the same time period he did, in predominantly Catholic New Orleans. He has every reason to believe she'd be just as horrified by him being homosexual as he is..
The whole set up of the world. The gods are petulant jerks whose petty whims and feuding causes untold suffering in the mortal world. Gods often take their frustrations out on mortals deserved or not. Olympus tends to be on the brink of imploding at least once a year. The gods can get away with nearly anything with mortals almost always in the wrong. Where you go in the underworld is largely determined by how the gods feel about you even if being an enemy of theirs is just. The alternatives to these gods is usually far worse. And Zeus, the one charged with keeping everything together, is the worse of the lot with being an arrogant moron to boot.
Not much of a fridge, as it's pointed out in Percy Jackson's Greek Gods: "You want scary? Zeus was the god of justice, oaths and promises. Which means the guy who zapped everyone who offended him and couldn't even keep his marriage vows was the one in charge of making sure kings and ambassadors were respected, rules obeyed, and vows kept. That's like making me the god of homework and good grades!"
So in The Son of Neptune we find out Hazel actually died in the 1940's and was offered Elysium, but turned it down as it meant her mother would go to the Fields of Punishment. So the judges split the punishment and sent the both to the Fields of Asphodel, a place where everyone forgets everything and just kind of exist in a dream scape...except Hazel. Being a daughter of Pluto, she remembers who she is and why she is there. The fields hold no power over her, except that she can't leave. She was there for 70 years before Nico busted her out, but most likely remembers most of it.
Nico originally wanted to bust Bianca out, as he sensed back in The Titan's Curse that she herself had gone to the Fields of Asphodel. Since Bianca was also a daughter of Hades/Pluto, she may have chosen reincarnation because she couldn't handle the stress of remembering everything the way Hazel did.
Hazel and Nico are both from before 1950. They get along really well, but of all the demigods, Hazel is the most likely one to have a problem with Nico being LGBT. In The Mark Of Athena, when Narcissus said 'I love him, he's so gorgeous', Hazel is specifically stated to have been appalled. Should Nico come out during the fifth book, things might not go so well between them. This is probably also why Nico has issues with being gay. It would also explain his sudden increase in showing physical affection towards Hazel, as noted when Nico gives Hazel peck on the cheek in front of the others. He's trying to soften the impact, should he eventually choose to come out to her, hoping that their bond has improved by that point that she won't turn him away.
In ancient Greece, homosexuality was heavily codified, and was essentially accepted in the form of an older man teaching to a younger one what love were, so Nico hence has all the reasons to have problems to come to terms with it, being from the greek's side of the gods, feeling attraction for someone who's about his age and being from the '30s. Romans, on the other hand, were definitely more open about it (the only thing that mattered was that romans were on top, and even that wasn't really necessary), that's both why Jason, being roman, has no problem in accepting Nico's sexuality, but also the reason the two gods bringing out homosexuality do it in their roman incarnation.
Except that Greecian homosexuality wasn't that heavily codified at all. Yes, an older man taking a younger one under his wing and teaching him "what love is" as you put it, was one of the ways it was commonly expressed. But it was far from the only way. In paticular, soldiers were encouraged and nearly expected to form sexual and romantic bonds with one another, because you would fight that much harder for the man at your side if you loved him than if he was just your comrade. And Nico and Percy were both soldiers in the Titan War, though they didn't fight side-by-side, Nico DID find out how to make him invulnerable
One of the big themes of the series is that the Greek and Roman camps become much more powerful when combined. And as Frank pointed out, the Byzantine Empire, which always was kind of a blend of Greek and Roman, lasted nearly a millennium longer than the Western Empire.
There are several occasions where Hazel calls up wealth without triggering her curse. For example, when she summons the Imperial Gold weapons from the bottom of the bay, when she calls up gold to feed Arion, and when she calls up a mound of schist to get a safehaven from the karpoi. Thinking about it, the one thing that all these scenes (and every other one where her summoned valuables are safe to touch), is that the summoned wealth is not going to be used as wealth. The Imperial Gold weapons weren't being used as gold, but as weapons and armor. The schist wasn't important because it was a precious stone, but because it was something that plants couldn't grow on. Now consider that Pluto stated that it was Marie's greed that brought down the curse, and it all makes sense. The curse was never tied to the riches themselves, it was tied to greed. Take up the riches for some reason other than avarice, for some purpose other than to spend them, and they are safe.
The gods acquired their Roman aspects after the flame of Western civilization moved to Rome, right? Then how can Aeneas, who survived the Trojan War, be the first of the Roman demigods? Rome wouldn't even be founded for another couple hundred years.
He was referred to as the founder of what would eventually become Rome. It's not too much of a stretch to imagine that some people would hear that and think of him as a Roman demigod.
Why could Percy remember Annabeth's name and face? Because she was his link to the mortal world when got the Curse of Achilles.
Word of God says that the remembrance was more from their bond.
Given how infamous the Roman punishment for patricide was, one has to wonder why Riordan left out most of the animals involved.
Leo is the seventh wheel, not because he doesn't have an official romantic partner on the Argo II, but because he represents two halves of of the Greek and Roman aspects of language into one. Remember, Leo knows Ancient Greek, but he has Latino heritage, making him susceptible to understand both languages with ease.
It's heavily implied that Hitler was one of Hades' children, thereby making him Nico and Hazel's half-brother. While most demigods are likely half-siblings with some monstrous historical figure or another, Nico and Hazel were actually alive during the reign of Nazi Germany. If things had played out a little differently, they could have been killed on behalf of their own brother.
In The Son of Neptune, Reyna mentions that she and Hylla were kidnapped by the pirates Percy released and held prisoner for months. Two young girls held by a bunch of deprived and depraved pirates... The implications aren't good at all.
No, she mentions that they learned to fight quickly and so were able to defend themselves. The implications if they didn't, though, are still there.
Reyna and Hylla learned to fight quickly, yes. They weren't the only women from Cerce's spa who got kidnapped, though...
Jason falls in love with Piper while amnesiac, taken away from someone named "Reyna". Now, if Percy's made any "friends" where he is...
This seems to have been Averted, as in the very first chapter of The Son of Neptune, Annabeth is really the only thing Percy remembers.
Fridge Brilliance: Reyna states that she wasn't involved with Jason, yet. However, Percy and Annabeth were very involved. In fact, their involvement lasted for two months before it was abruptly cut short by Hera/Juno. It is not unheard of for amnesia victims to remember faces and names of loved ones.
Even more importantly, Hera is the goddess of marriage. She wouldn't separate two lovers.
Nemesis always takes the form of whoever the person looking at her hates the most. Since we know she's had at least one demigod child from the last series, this raises the question: Who has sex with someone who looks like their worst enemy?
Maybe Nemesis is into bondage as a sub? Dominating your worst enemy would definitely be something some people would be into...
Charmspeak is a horrifying ability. If you wonder why check Jessica Jones. Piper is a good character, but man she's got the most horrible ability.
Not so much, Piper notes in House of Hades that just laying on the charmspeak and telling people what to do makes it less effective. It works much better if she's telling people to do something they already want to do.