Mistakes in the Series (CHB)

"They know this stuff and I have to really keep on top of this because if I do make a mistake or make a reference that’s wrong, they’ll catch me. They’re very perceptive about everything mythology."

- Rick Riordan

Despite Rick Riordan's best intentions, there are mistakes in the Percy Jackson and the Olympians series and The Heroes of Olympus series, either based on continuity or character flaws. While some of these have explanations, even coming from Rick Riordan himself on his blog or Twitter, not all are explained directly in the books and can still be considered mistakes. There are also other errors in the series that may never be explained and can only be considered mistakes.

The Lightning Thief

 * Sally Jackson says that Poseidon was only with her for the summer. However, it is mentioned that Percy's birthday is August 18th, which is during the summer. This would mean that Poseidon and Sally would have to have been together around December for Percy to be born in August.
 * Before Ares decides to battle Percy himself, he sends a wild boar to attack him. Percy notes that the boar is "even larger and uglier than the one whose head hung above the door on cabin seven". However, cabin seven is Apollo's. Ares' cabin is cabin five. This could have been a typo on Rick Riordan's part.

The Sea of Monsters

 * The Gray sisters mention they met Jason yet they're never mentioned in Jason and the Argonauts. It's possible Rick Riordan meant to say Perseus (Percy's namesake).
 * While riding in the Gray Sisters' Taxi, Tempest constantly asks for the eye from Wasp despite Anger being the one with the eye. However, even though Anger had the eye, Wasp managed to warn Tempest to move before crashing the taxi.
 * It is possible that because Tempest didn't have the eye, she couldn't see which of her sisters had the eye at the time. How Wasp managed to warn Tempest without the eye before they crashed is unknown.
 * Thalia Grace appears in Percy's dreams during the story. In his dreams, she is described as having green eyes. However, when she is revived and appears in later stories, her eyes are said to be blue.
 * This could simply be because it was in a dream and that is how Thalia appeared, but this is unconfirmed.
 * Annabeth Chase tells Percy that she knows parts of the Great Prophecy, but not the complete prophecy. Later in the series, she mentions knowing the prophecy in its entirety, and that it still gives her nightmares.
 * She may have learned the full prophecy later in the series. However, in The Last Olympian, she says she read it when she was nine years old, and she was thirteen in The Sea of Monsters.
 * While saving Blackjack from the Princess Andromeda, Percy calls Blackjack a mare (a female horse). However, Blackjack is a male in all other appearances.
 * During a Q&A on Rick Riordan's Twitter account, he stated that Percy didn't know Blackjack was male at the time. This mistake is never addressed by Percy or Blackjack in the series however.
 * Annabeth tells the story of the Golden Fleece using the names Cadmus and Europa when it should have been Phrixus and Helle.
 * Percy's plan to keep him and Annabeth inside an air bubble to prevent her from listening to the Sirens shouldn't have worked because, after crossing into the bubble, the soundwaves would go back to traveling as they did above the surface and therefore Annabeth would've been able to understand the music.

The Titan's Curse

 * Hades is not at the Winter Solstice meeting on Olympus, even though this is the only time he is allowed on Olympus and has to attend the meeting.
 * This could simply mean Percy did not see him, although he is not mentioned having voted either.
 * Percy inquires whether or not it would be possible to contact a god via Iris Message. He had already done this when he contacted Dionysus while aboard the Princess Andromeda in The Sea of Monsters.
 * As Atlas explains the necessity in lifting the sky stems from Gaea's and Ouranos's attempt to reconcile, Gaea is spelled with an i.

The Battle of the Labyrinth

 * Strangely, when Chiron called a war council at the sword arena before Annabeth's quest, the head counselors of Demeter and Dionysus cabin were not present.
 * Percy may have just not seen them when Chiron called the meeting.
 * As Percy is about to fight Antaeus, Annabeth yelled "His mother is Gaia!" However, in The Heroes of Olympus series, it is always spelled Gaea, with an e and not an i.
 * This may be a result of the author forgetting how he spelled it, as the word Gaea has multiple spellings.

The Sword of Hades

 * During their trek through the Underworld with Nico di Angelo, Percy thinks to himself that because Thalia is now immortal, she had not aged since about a year ago, and that would mean he was now older than her. However, Thalia was a day younger than sixteen when she became a Hunter in The Titan's Curse, and since The Sword of Hades takes place on Christmas Day of the same year as The Battle of the Labyrinth, Percy would only be about fifteen and a half, and therefore younger than Thalia.
 * It is possible that this miscalculation had to do with poor math skills on Percy's part.

The Last Olympian

 * Silena Beauregard's hair and eye color change from the color mentioned in The Demigod Files.
 * It is possible that because Silena is a daughter of Aphrodite, her hair and eye color can change naturally, like Aphrodite.
 * It is revealed that after Zeus had tried to kill Bianca and Nico di Angelo, Hades had the two placed in the Lotus Hotel and Casino, giving him the possibility to use them to control the Great Prophecy, as the demigods would not age once inside. However, they were placed inside when they were infants, so it is unknown how they grew to the ages they are at in The Titan's Curse.
 * It is possible that they were not placed directly in the Lotus Hotel, as Bianca seems to have some memory of living in Washington D.C. in the past.
 * When Percy Jackson starts fighting the Clazmonian Sow, he correctly calls it "her". However, when Percy is giving Blackjack instructions further on in the fight against the sow, he says "Get in front of the pig. Taunt him!".
 * Connor Stoll's name is spelled 'Conner' whereas in the rest of the series it's been spelled 'Connor'.
 * The end of the Second Olympian War and the completion of the first Great Prophecy happened on August 18, Percy's birthday. However because of the days he spent in the Lotus Hotel and Casino, Percy is actually five days younger than sixteen, making the prophecy inaccurate.
 * When Hestia is showing Percy a flashback of when May Castellan is trying to inherit the spirit of Delphi, he says it is Camp Half-Blood in a different generation, the 1990's. However, during this period, Luke Castellan is a baby, born in 1986, meaning the year was either 1986 or 1987.
 * This could just be Percy's misinterpretation of the era, and a rough guess on his part.

The Lost Hero

 * While Jason Grace is given a tour of Camp Half-Blood, it is said that all the new cabins were built last year. However, The Lost Hero takes place only four months after The Last Olympian.
 * Nyssa tells Leo Valdez that Charles Beckendorf found the Bronze Dragon in pieces and rebuilt it. However, in The Demigod Files, Percy Jackson, Annabeth Chase, and Silena Beauregard were the ones who found the dragon, and Annabeth fixed it.
 * Nyssa may not have known the full details of how the dragon was found, and therefore assumed that Beckendorf had been the one who fixed it.
 * Or, after Beckendorf managed to subdue it, the Dragon might have fallen apart once more, and was eventually repaired by Beckendorf, this time properly.
 * Rachel Elizabeth Dare is said to be going to Clarion Ladies Academy in New Hampshire. However, in The Last Olympian, Clarion Ladies Academy is said to be in Connecticut.
 * While Jason is looking at the old photo of Annabeth, Luke Castellan, and Thalia Grace in Cabin One, it is said that in the photo Thalia was "maybe fifteen"- however, Thalia couldn't have been any older than twelve or thirteen at the time the photo was taken.
 * It is possible that Thalia could have looked mature for her age.
 * Tartarus is misspelled as “Tatarus” on page 508.
 * Enceladus claimed to be the shortest and smallest Giant of all, being "only" 30 ft tall. However, in The Son of Neptune, Polybotes is no taller, and in The House of Hades, Damasen and Clytius are both shorter, being only 20 ft tall. Still, the two shortest Giants of all are in fact Otis and Ephialtes, who are only 12 ft tall.
 * When Jason's memories return, he mentions Hazel as a good friend of his. However, in The House of Hades, Hazel admits that she has a hard time warming up to him, and that she can't get a read on him. Overall, Jason seems to be more of a legend to her than an actual person, and she would rather be accompanied by Frank, Nico, Piper or Leo than Jason. This implies that the two barely knew each other before Jason disappears.
 * In the gods section in The Lost Hero, Aphrodite is said to be 'marred' to Hephaestus. 'Marred' means to inflict serious damage, so the correct word should have been 'married'.

The Son of Neptune

 * Percy yells at Hera for taking eight months of his life from him. However, Percy was only gone for six months, as he vanished from Camp Half-Blood on December 13 and then appeared at Camp Jupiter in late June.
 * Percy might have thought that he was gone that long, because Jason went missing from the Roman Camp in October, eight months before the book's events. Percy finds out he was only gone for six months in the next book.
 * Percy is being chased by Stheno and Euryale, the gorgon sisters of Medusa. Meanwhile in The Lightning Thief, Medusa mentions to Percy that her sisters had faded (which is the equivalent of permanently dying for immortals and monsters) after being forgotten in her shadow.
 * However, Euryale says that Gaea brought them back, so there is a possibility that Gaea's powers include bringing back monsters after they fade. Or, they could of returned via the Doors of Death, which is the reason why they never stayed dead very long.


 * In some editions of the book, Julia's name is once misspelled as "Juila."

The Diary of Luke Castellan

 * In The Demigod Diaries, it is mentioned in the weapons section that Thalia's shield Aegis was given to her by Athena. However, in this story, it is revealed that they found it in Halcyon Green's mansion.

Leo Valdez and the Quest for Buford

 * It is mentioned that Leo has been working on the Argo II for two months, despite this story taking place less than a week after the events of The Lost Hero.

The Mark of Athena

 * Soon after the Argo II arrives at Camp Jupiter, it is mentioned that Hylla had left earlier in the morning. However, Hylla was present in the Senate meeting when the Argo II first arrived at the camp. However, she might have left right afterwards.
 * Soon after the Argo II is forced to flee from Camp Jupiter, Percy sees the sun set over a live feed of Camp Half-Blood. However, at the time it was only early afternoon at the camp during the summer, making a sunset very unlikely.
 * Though this could just be because of the time change between California and Long Island, the locations of each camps.


 * Hazel Levesque mentions to Leo that she had not had a flashback in a long time. However, she only refrained from having a flashback for a few days at this point. Even during The Son of Neptune when they were supposedly at their worst, she still only had one a day at most.
 * Hazel may have ADHD, making it seem longer. This is unconfirmed however, as children in the 1940s with ADHD would have been called lazy instead.


 * Alcyoneus states in The Son of Neptune that he must rise before any of his fellow Gigantes, as he is the oldest. However, Otis and Ephialtes have been helping Arachne capture demigods for centuries.
 * It is possible that Otis and Ephialtes never truly rose, as they made a home under the surface of Rome.


 * While Piper and Jason are talking to Bacchus, the god mentions how he had fought alongside Heracles. However, Heracles is the Greek name for the Roman god Hercules.
 * It is possible he mixed up the names, as his Greek and Roman sides were both struggling for control at the time.


 * Percy mentions that he knew the Romans for weeks. However, by this point in the series he had only known the Romans for about ten days, including the time he spent with Frank and Hazel on his quest.
 * Since he had amnesia at the time, Percy's perception of time might have been altered.


 * Hercules warns Piper and Jason that he will kill them and their friends on the Argo II if they try and contact them. Later when Piper thinks of a plan to pass Hercules without giving him the Cornucopia, she uses an Iris Message to contact them.
 * It is possible that Hercules simply got distracted and didn't notice the message.


 * Frank Zhang mentions in The Son of Neptune that the only Chinese character he knows is his family name. However, in The Mark of Athena he is able to read enough Chinese to find a location marked on a map by a Chinese tourist.


 * Percy mentions that it has been five years since he arrived at Camp Half-Blood. However, The Mark of Athena only takes place four years after the events of The Lightning Thief.


 * Percy mentions that he has met Persephone once, but he has actually met her twice: once in The Demigod Files and once in The Last Olympian.


 * Gaea claimed that Sammy died in the 1960s of a heart attack in The Son of Neptune. However, Leo Valdez, Sammy's great grandson, was born before Sammy died, meaning Leo would be over 30 years-old if this was true. Hazel later confirms that that Gaea's earlier claim was a lie.
 * It is very possible that Gaea was lying to manipulate Hazel.
 * Percy claims that Chrysaor is just as good of a swordsman as Ares himself. However, since Percy was able to defeat the god of war in a sword fight, and has increased in power since then, it is unlikely that Chrysaor would have been able to defeat him so easily.
 * Leo comments on how the discovery of the Archimedes sphere saying that it is bigger than Daedalus' laptop. However, it is spelled "Daedlus's."
 * In this book Annabeth claims to be the "magna mater" of the Athena sisterhood, while in The Staff of Serapis she claims to have been the "magna mater" of the Athena cult.
 * Annabeth might have forgotten the original title that she had given herself at the time.

The House of Hades

 * Hazel mentions that Gaea forced her to raise Porphyrion when she lived in Alaska. But she actually raised Alcyoneus.
 * The bright red Fiat 500 that knocked Arachne into Tartarus at the end of The Mark of Athena is described as baby blue here.
 * Piper McLean mistakenly referred her Dad's old assistant as Jessica. In The Lost Hero, the assistant's name was Jane.
 * On Rick Riordan's Twitter page, he answers a question regarding her name change. He states that he simply forgot her name.
 * When Rachel Elizabeth Dare meets with Reyna and Octavian at the top of the Empire State Building, she calls Octavian a son of Apollo when in previous books, he is referred to as a Legacy. Strangely, Octavian does not correct her.
 * Rick explained on his Twitter that calling Octavian a son of Apollo is honorific, and compared it to calling mankind "sons of Adam", when they are actually descendants of him.
 * Leo yells at Gaea that she lied to him about his great grandfather having died in the 1960s. Actually, she lied to Hazel, not Leo.
 * At the start of chapter 2, Hazel compares the joy of seeing Arion to her first kiss with Frank, which in her thoughts happened after the battle of New Rome.  However in The Son of Neptune, they first kiss up in Alaska after Frank kills the giant.
 * However, they might have kissed again after the battle, and Hazel considers it to be the "first" kiss of their relationship, since Frank was initially uneasy during their first actual kiss.
 * It is said that Leo's army jacket burned up. However, in The Lost Hero, when Aphrodite gives them a makeover before they battle Enceladus, she takes his army jacket, and swaps it for a dress shirt, suspenders, and trousers.
 * Nico claims that Hades had meet his mother in Venice, however, in The Last Olympian, Hades himself claims to have meet her in Washington DC.
 * When Ares and Mars are arguing, Mars refers to Heracles, but being Roman, it should have been Hercules.
 * It is possible he mixed up the names, as his Greek and Roman sides were both struggling for control at the time inside of Frank's head.
 * Nico bitterly says that since he is a son of Hades, he has no friends and "might as well be covered in blood or sewage", judging from how almost all other demigods fear and hate him. However, in The Last Olympian, after Nico helps save Olympus, Percy states that everybody acted friendly with him, and complimented his amazing fighting skills, and even the Ares demigods consider him "pretty cool".
 * However, Nico could be using this as cover for his overwhelming fear of coming out of the closet.