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

 * The American cover shows Percy in Long Island Sound holding Riptide and the Minotaur's horn. However, this scene is never shown in the book.

The Sea of Monsters

 * 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.


 * 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.

The Titan's Curse

 * Hades is not at the Winter Solstice, even though this is the only time he is allowed and has to attend the meeting.
 * This could simply mean Percy did not see him.

The Battle of the Labyrinth

 * Percy mentioned that three years ago, when he had started camp, there was more than a hundred campers; however, he had only spent two years at camp.
 * 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.
 * The American cover shows Percy standing by Kronos' Coffin, but in the book he is wearing Annabeth's Yankees Cap, making him invisible.
 * 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 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.


 * 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.

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, during the same year.


 * While Jason is fighting Porphyrion, he mentions being the leader of the First Legion. However, it is said in The Son of Neptune that Camp Jupiter is composed of the Twelfth Legion.
 * It is possible that Jason got this wrong as a result of his memories being stolen from him.


 * 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 Grace is looking at the old photo of Annabeth Chase, 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.
 * The American Cover shows that Piper McLean still has Aphrodite's Blessing and is wearing a dress. However at this point in the book she has almost fully lost the blessing and had changed out of the dress before she left.

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 13th and then appeared at Camp Jupiter in late June.


 * 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.


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

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.
 * This might be due to Leo's ADHD and how long he works.

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.
 * Hylla might have left after seeing the ship
 * 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.
 * 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 along side Heracles. However, Heracles is the Greek name for the Roman god Hercules.
 * Maybe the greek/roman names was too much for Piper and Jason so they accidently made a mix of greek/roman names in their conversation
 * 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.
 * It might have been the cause of Percy's ADHD
 * At one point, Leo sets his clothes partially on fire when he is woken up by a large ship. However, his clothes have been immune to fire every other time in the series.
 * 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 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.
 * It is very possible that Gaea was lying to manipulate Hazel.