“ | 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, during an interview with EW. |
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. Rick Riordan has stated that the books don't exist in any specific year so no more notes about timeline facts and mistakes if it is about a reference that would have come after or before the book takes place.
Percy Jackson and the Olympians
The Lightning Thief
- Sally Jackson mentions that she was with Poseidon for one summer, but Percy's birthday is August 18, which is the next summer, much longer than a usual pregnancy.
- In The Chalice of the Gods, Sally mentions that Percy came much later than expected.
- Luke mentions that some of the things that Hermes represents are "Messengers. Medicine. Travelers", though Hermes is not the god of medicine, Apollo is.
- Luke claims to have only seen Hermes once in his life when he was 14. However, since Luke attended the campers field trip to Olympus during the Winter Solstice (during which all of the Olympians must be present), he should have seen Hermes there as well. It is also said that when Annabeth and Thalia came back with him in a flashback shown by Hestia that Luke has visited him more than once. It is also possible that it was even more times, as Hermes visited May Castellan, Luke's mother.
- It is possible that despite chaperoning the trip, Luke never went into the throne room with everyone else, and instead was off taking the master bolt.
- It is also possible that he was 14 on the trip to Olympus, but this is highly unlikely.
- It is physically impossible to fall from the Gateway Arch in St. Louis into the Mississippi River, as the Gateway Arch does not span the river. However, Percy Jackson supposedly did so in The Lightning Thief. It is in fact almost five hundred feet from the edge of the Mississippi River normally. Falling straight down would land Percy in the middle of the grassy park of the Jefferson National Expansion Memorial. Though Poseidon and/or Zeus may have been helping him, knowing he would be vital to future prophecies.
- When Chiron reminds Percy of Poseidon and Hera's unsuccessful Olympian riot against Zeus (which was addressed in question 38 of his final exam), Percy recalls that Zeus was trapped in a golden net. However, in Percy Jackson's Greek Gods, it is revealed to have been a magical rope instead.
- This could have been Rick Riordan showing how basic Percy's knowledge of mythology was.
- When Chiron corrects Percy's mistakes about Kronos and the Titanomachy, he mentions that the extremely powerful emetic Zeus gave Kronos was "a mixture of mustard and wine," while in Percy Jackson's Greek Gods, it is actually revealed to have been a mixture of mustard and nectar. In any case, Zeus could not have used wine, since that particular beverage was invented by his son Dionysus, many years after the Titanomachy.
- In the Kindness International truck in which Ares had helped Percy, Grover and Annabeth get into, Percy has a dream about Thalia Grace and states that she had "dark eyeliner around stormy green eyes" but at the end of The Sea of Monsters as well as all later books, Thalia is described with blue eyes.
The Sea of Monsters
- The Gray sisters say they've met and served 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. But 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 stormy green eyes. However, when she is revived and appears in later stories, her eyes are said to be electric blue.
- When asked this question by his fans, Rick Riordan admitted that this was an error on his part.
- 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.
- Annabeth could have been lying to avoid being questioned any further.
- 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.
- 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. Considering Annabeth's vast knowledge of Greek mythology, such a big error is surprising (of course, it was an error on Rick's part, not Annabeth's).
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, or if Hades did not go, due to his hate towards the Olympians
- Percy inquires whether or not it would be possible to contact a god via Iris Message. But, he had already done so when he contacted Dionysus while aboard the Princess Andromeda in The Sea of Monsters.
- Given that Dionysus runs Camp Half-Blood and therefore spends more time in the mortal world than other gods, Percy might have believed that he simply abode by different rules than the other gods.
- When Ares curses Percy's sword in The Lightning Thief, he says "Every time you raise your blade in battle, every time you hope for success, you will feel my curse. Beware, Perseus Jackson!" However when the curse is activated, Percy remembers it as "When you need it most, your sword will fail you."
- Percy might not recall the exact words of Ares' curse.
- Also, the curse only takes hold during his fight with Atlas, despite Percy using his sword in other battles with no ill effects. It is possible that Ares meant that his curse could take hold at any time and to remember that every time he went into battle.
- Thalia states that the apples of immortality were a wedding gift to Hera from Zeus, when in fact, they were given by Gaea (as seen in Percy Jackson's Greek Gods).
The Battle of the Labyrinth
- When heading to Grover's hearing, Percy sees the dining hall and mentions that he hasn't seen the place since last summer. This is not true, however, as The Titan's Curse took place just the winter before.
- Strangely, when Chiron called a war council at the sword arena before Annabeth's quest, the head counselors of the Demeter and Dionysus cabins were not present.
- Percy may have just not seen them when Chiron called the meeting.
- Percy mentioned the cabin inspection took place every afternoon, but in The Last Olympian and Rick's official website, the cabin inspection took place in the morning.
- The Telekhines claim to have been the ones to forge Poseidon's mighty Trident. However, in Percy Jackson's Greek Gods, the Trident is shown to have been made by the Elder Cyclopes.
- Tyson claims that Briares, as a Hekatonkheire giant, is older than Cyclopes. However in Percy Jackson's Greek Gods, the three Hekatonkheires are stated to have been born to Gaea and Ouranos after the Elder Cyclopes.
- Annabeth tells Percy that she was a brain-child, born from Athena's mind, but in Percy Jackson's Greek Gods, Percy says he has never asked, implying he does not know if Annabeth was born from a handkerchief, which is not true.
- After the battle, Daedalus is wounded and Mrs. O'Leary licks at his wounds. However, a typo appears in the first edition of the book, which reads, "Mrs. O’Leary loomed behind him, licking the wounds on his master’s head so Daedalus’s hair stood up funny" (Riordan, 333). This is a mistake, as Mrs. O'Leary is female.
- This mistake was still present in the first paperback printing by Scholastic in September 2009.
- This mistake is also present in the audiobook version narrated by Jesse Bernstein, (Ch. 18, min. 26:00).
- The error seems to have been corrected in later printings and on the eBook versions.
The Demigod Files
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 still younger than Thalia.
- In The Sword of Hades, Nico says Sisyphus tricked Persephone. In Percy Jackson's Greek Gods, Percy claims Sisyphus tricked Hades.
- He could have tricked both.
The Last Olympian
- Silena Beauregard's hair and eye color change from the color mentioned in The Demigod Files, as well as having a different hair and eye color in The Ultimate Guide.
- It is possible that because Silena is a daughter of Aphrodite, her hair and eye color can change naturally like Aphrodite, though it is never mentioned or showed to be an actual power for any of her demigod children. (Excluding Piper Mclean, whose eyes "seemed to change color like a kaleidoscope.")
- Hestia, when speaking with Nico and Percy outside May Castellan's house, agrees with Percy that she gave up her seat for Dionysus. However, in Percy Jackson's Greek Gods, Percy says that Hestia didn't even take a seat in the Olympian Council.
- When Percy gets a call from Silena about Annabeth after she got stabbed, Percy mentions the Caller ID on his mother's cell phone to be from Finklestein & Associates, but cell phones don't have Caller ID like landlines do, even to this day. On cell phones, when someone calls you, it only shows the number, never the name of the person calling unless it's listed on your contacts.
- It's possible that Percy's mom has that number listed on her contacts.
- 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 very small children, so it is unknown how they grew to the ages they are at in The Titan's Curse, because from the looks of it they were not out for more than two years before coming to the camp.
- It is possible that they were removed from the Lotus Hotel and Casino after Zeus broke the vow the first time, giving them nearly seven years' time to age by The Titan's Curse.
- 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!"
- He could have been randomly picking pronouns.
- 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.
- The prophecy could have meant chronologically from the date of birth rather than biologically.
- If so, Hades' plans to make Nico the hero of the Prophecy would not work.
- The prophecy could have meant chronologically from the date of birth rather than biologically.
- 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, though it may have been years after Luke was born.
- In The Last Olympian, Krios' armor was described as being black, while Percy Jackson's Greek Gods claims that it was "navy blue."
- In the House of Hades, Percy mentions seeing the "navy blue" armor.
- It might be because navy blue is similar to black and Percy didn't see it clearly.
- When Hestia and Percy talk, she claims that she gave her throne to Dionysus to prevent a war among the gods. This is odd considering that in Percy Jackson's Greek Gods, Hestia was too modest to accept having a throne in the first place.
Percy Jackson's Greek Gods
Based on the nature of the book being about Percy recounting certain myths and adding "his own magic--and sarcastic asides--to the classics," certain information from the book may contradict with information from the main series of stories. As a result, if something is mentioned in this book that is mentioned differently in the series, please add it below.
The Heroes of Olympus
The Lost Hero
- When the flying chariot is crashed at Camp Half-Blood, Will Solace and the Apollo cabin are implied to own it. However, in The Last Olympian, the dispute between the Ares and Apollo cabins over who owned the chariot ultimately resulted in it being property of the Ares cabin, not Apollo.
- It is possible that the Ares Cabin gave it back to the Apollo cabin after the Battle of Manhattan.
- 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 fight on Mt. Diablo, Enceladus mentions that Jason had killed the Titan Krios. This is contradictory to what Hermes told Percy, that Titans cannot be killed.
- It is likely that Hermes meant "kill" in a more permanent sense, while Enceladus meant that Jason had sent Krios to reform in Tartarus.
- 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 Connecticut. However, in The Last Olympian, Clarion Ladies Academy is said to be in New Hampshire, though there may be many branches of the school.
- While Jason 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.
- Enceladus claimed to be the shortest and smallest giant of all, being "only" 30 feet 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 feet tall. In The Mark of Athena, Otis and Ephialtes are only 12 feet tall. Even their combined height is still considerably shorter than Enceladus's. Still, the shortest Giant of all is, in fact, Orion, who is short enough to be mistaken for a human.
- 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 disappeared, though he may have considered her a friend while she didn't return the feeling.
- Hera/Juno told Jason that gods never experience dreams. This is contrary to Ares' confession that he is having dreams about 'someone' who whispered him words that will break his family apart.
- This might be due to the fact that Kronos has more power than whatever makes demigods experience dreams.
- When Jason is boasting to Porphyrion, he says that he is praetor to the first legion. However, Camp Jupiter is the Twelfth Legion, not the first.
- However, it is mentioned that Jason had tried to change the name of the legion from the twelfth to the first.
- Hera mentions that she and Zeus only have two children (Ares and Hephaestus). However in Percy Jackson's Greek Gods, Hera and Zeus are mentioned to also have Hebe (the goddess of youth), Enyo (the goddess of war), and Eileithyia (the goddess of childbirth) as daughters, and Ares is their only son, as Hephaestus was conceived by Hera alone.
- It's possible Hera was simply referring to having only two children of her own on the Olympian Council or possibly only talking about her sons.
The Son of Neptune
- Reyna has four bar lines on her SPQR tattoo, representing four years of service to the 12th Legion. However, she did not join the Legion until after the events of The Sea of Monsters, which took place only 3 years before.
- Thanatos tells Frank that they will meet again in unfavorable circumstances. However, this meeting does not occur at all, even until the end of the series.
- It could be when Frank is older, or when he is dying.
- It could also have something to do with when Frank's stick burns up in The Tyrant's Tomb.
- 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. He eventually realized his error in The Mark of Athena.
- It is also possible that he is talking about the entire time his memories were away, which could have also been during his stay in New Rome.
- 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 have returned via the Doors of Death, which is the reason why they never stayed dead very long.
- Medusa says her sisters have "passed on," meaning that they may not have faded and were only reforming at the time of The Lightning Thief.
- Octavian gave Frank the Mural Crown for being the first over the walls in siege warfare. However, the Mural Crown was described as a "bronze badge shaped like a laurel wreath." In ancient Rome, the Mural Crown was a golden crown that resembled a battlement.
- Otrera is referred to as a daughter of Ares, but in Percy Jackson's Greek Heroes, Otrera is Ares's consort, not his daughter.
- Due to the ways godly families work, she could be both, though this almost never happens even among gods.
The Demigod Diaries
The Diary of Luke Castellan
- Thalia said that Amaltheia led her to find Luke the night that she ran away. But Thalia said that she ran away when Jason disappeared when he was two, and since she was seven when he was born, that would've made her nine years old. However, Thalia and Luke only knew each other a few months before they met Annabeth, and they were 12 and 14 years old.
Greeks And Romans
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 at Christmas Eve, which is 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.
- Soon after the Argo II is forced to flee from Camp Jupiter, Percy sees the sunset over a live feed of Camp Half-Blood. However at the time, it was early afternoon at Camp Jupiter and with only a four-hour difference between camps, it is unlikely that it was a sunset.
- 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.
- 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.
- Nemesis claims that she is called Nemesis in both Greek/Roman Forms while her Roman form is actually called Invidia.
- While Piper and Jason are talking to Bacchus, the god mentions how he had fought alongside Heracles (who he calls "Harry Cleese"). However, Heracles is the Greek name for the Roman god Hercules.
- This could be due to Bacchus's tendency to get names wrong. Notably, his Greek form, Dionysus, refers to the god as "Hercules" in the previous series.
- While talking to Bacchus, Piper refers to him as Dionysus even though he was in his Roman form. Although it was not to his face.
- 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.
- He could have been including his time with Lupa.
- 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.
- Percy refers to the Curse of Achilles as the blessing of Achilles instead even though it is known as the Curse of Achilles.
- 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 less than four years after the events of The Lightning Thief.
- He could have remembered wrong.
- 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.
- He could have remembered wrong.
- Leo Valdez comments on the discovery of the Archimedes sphere, saying that it is bigger than Daedalus' laptop. However, it it is spelled "Daedlus's."
- This may be because Leo is dyslexic, so he isn't very good at spelling.
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 later described as baby blue.
- Piper McLean mistakenly referred to 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. [1][2]
- 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. 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 Valdez yells at Gaea that she lied to him about his great grandfather having died in the 1960s. Gaea actually lied to Hazel, not Leo.
- At the start of chapter 2, Hazel compares the joy of seeing Arion to her first kiss with Frank Zhang, which in her thoughts happened after the battle of New Rome. However, in The Son of Neptune, they supposedly have their 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 actual first kiss.
- Nico di Angelo said that him and his, now deceased sister, Bianca di Angelo, stayed in the Lotus Hotel for about a month, while Bianca said in The Titan's Curse that they stayed there for about an hour.
- Bianca's perception of time within the casino might have been different from Nico's, since she was older.
- 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.
- Leo may have recovered the jacket later somehow and then burned it.
- Nico di Angelo claims that Hades had met his mother in Venice. However in The Last Olympian, Hades himself claims to have meet her in Washington, D.C..
- 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.
- Krios says that Jason Grace killed him on Mount Othrys. However, this contradicts Chiron's claim in The Lightning Thief that the Titans are alive but imprisoned and Poseidon telling Percy that the Titans cannot die any more than the gods can.
- Jason cannot recall the story of Calypso when he realizes that was where Leo had disappeared to, believing her to be an evil sorceress. Yet according to Leo, Piper had told Jason about Percy's time with Calypso after she had heard it from Annabeth.
- He could have forgotten.
- Jason mentioned that he offered Percy Jackson his role of praetor, but Percy was the one who offered to step aside for Jason.
- Nyx claims that the Fates are her children, while in Percy Jackson's Greek Gods it is established that they are the children of Zeus and Themis, the Titaness of Divine Law and Justice.
- Nyx claims that the goddess Hecate is her daughter, despite the fact that it was established that she is the daughter of the Titans Perses and Asteria by Hecate herself in the same book.
The Blood of Olympus
- Annabeth's drakon bone sword is called a dragon bone sword. However, this is likely just a typo.
- Nico claims that he did not design the Hades cabin despite him designing and having it built in The Last Olympian. He goes on to complain about the cabin he designed himself.
- Other campers might have changed the way the cabin looked or rebuilt it, as Nico rarely visited Camp Half-Blood.
- Reyna states, while observing Octavian through a dream, that he had ignored her orders by moving the legion closer to Camp Half-Blood, however, her original orders only restricted the legion from attacking the Camp itself.
- It could be that Reyna just remembered wrong.
- Octavian is said to be aided by wolves and spirits in The House of Hades. However, neither the wolves nor the spirits make an appearence in the final battle and Reyna states that Lupa and her wolves would never side with Octavian.
- It could be that Octavian had deployed them elsewhere.
- Reyna stated earlier that Bryce was a legacy of Orcus. But when he catches her in Buford, he says Orcus is his father.
- It could be that Reyna just remembered wrong.
- Percy didn't understand when Frank said half a kilometer and needed Hazel to say five or six football fields when in The Battle of the Labyrinth, Percy himself used half a kilometer to say how far the nearest source of water was when he needed to extinguish the flames on Juniper's tree.
- It is possible that his water location abilities automatically gave him the required measurement.
- In chapter 26, page 257, it says "Kym narrowed" when it should say, "Kym's eyes narrowed".
- At the end of the book, it is mentioned that Percy and Annabeth would be starting their senior year (12th grade) together in NYC. However, Percy gets kidnapped and The Heroes of Olympus series begins only a few months after the end of The Last Olympian. This means he would have been kidnapped in the middle of his sophomore year (10th grade) as it's mentioned he had just completed his freshman year (9th grade) at the start of The Last Olympian. The entirety of The Heroes of Olympus takes place from December to August of that year, so Percy should only be starting 11th grade at the end of The Blood of Olympus. Additionally, he missed half of his 10th-grade year being kidnapped and missing, so he would be behind and would have to make that up.
- In The Hidden Oracle, he is at an alternative high school to finish his senior year.
The Staff of Serapis
- Annabeth claims to be the "magna mater" of the Athena sisterhood in The Mark of Athena, 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. But this is unlikely, seeing as Percy says that Annabeth rarely forgets anything in The Battle of the Labyrinth.
The Trials of Apollo
The Hidden Oracle
- In Chapter 5, the second line of the Haiku, "Chocolate chip cookies in blue" is eight syllables, not seven.
- It might be because "chocolate" sounds more like "chok-lat", not "cho-ko-lat".
- In Chapter 13, Apollo describes Harley as eight-years-old. Harley was also eight in The Lost Hero, and more than a year had passed. This means Harley should be 9 or even 10.
- In Chapter 20, Rachel says that she tried sending physical mail to Camp Jupiter, but got no response. In The Tyrant's Tomb, Reyna is able to easily send and receive mail despite the Triumvirate.
- However, it's also mentioned to take a long time between responses and Reyna was sending messages to the Hunters of Artemis via a Wyoming P.O. box rather than the other demigod camp on the other side of the country.
- In Chapter 22, Apollo recognizes Billie's seeds as geraniums. However, Apollo is shown to have pathetic botany skills and shouldn't have been able to recognize them.
- Later in Chapter 22, a myrmeke's shell is described as black. In Percy Jackson and the Bronze Dragon, the myrmekes have red shells.
- Different types of myrmekes could have different color shells.
- In Chapter 32, Nero uses some kind of oil to spark Greek Fire. However, Greek Fire just bursts into flame; it doesn't have any oil. Also, the fire is described as red later in the chapter, but Greek Fire is green.
- Apollo might have believed that it was Greek Fire even though it was not.
- In Chapter 35, Apollo narrates, "Her [Meg's] absence felt like a Colossus stomping upon my heart," and refers to this as a metaphor. This is a simile.
The Dark Prophecy
- In Chapter 12, Apollo mentions that Calypso knows very little about Rome, as she has no idea who Commodus was. In The House of Hades, she is able to easily identify a Roman Standard.
- In Chapter 24, Apollo sings a song from the Frozen soundtrack. Frozen came out a year after this book takes place.
- However, Apollo is also the god of prophecy, making it possible that he may be able to know songs before they come out.
- In Chapter 36, Apollo mentions that Nanette was hit by a crossbow turret. Actually, Nanette had been shot by Hemithea with an arrow.
The Burning Maze
- When Apollo says Caligula's full name in Chapter 9, he says "Gaius Julius Caesar Germanicus." He left out the word "Augustus".
- When Apollo says Caligula's full name in chapter 9, he mentions that multiple famous Romans shared his name. This is incorrect, only Caligula had the name Gaius Julius Caesar Augustus Germanicus.
- Apollo could be talking about the first three names only: Gaius Julius Caesar. There were multiple famous Romans whose name included those three names, notably Julius Caesar (Gaius Julius Caesar) Octavian the emperor, (Gaius Julius Caesar Octavianus) and Caligula. (Gaius Julius Caesar Augustus Germanicus.)
- In Chapter 23, Jason has a lightning bolt tattoo on his arm. The tattoo for children of Jupiter is an eagle, not a lightning bolt.
- In Chapter 26, Timbre and Crest are holding Apollo, Meg, Jason, and Piper at arrowpoint, with Peak holding his sword behind them. When Meg later attacks the pandai, Peak is holding a bow with Crest, and Timbre is the one with the sword.
- In Chapter 45, Grover says he has never met Reyna. However, they had actually met on Nero's Tower in The House of Hades.
- In Chapter 46, Apollo refers to he and Meg as ‘two teenagers’. However, Meg was twelve at that time.
The Tyrant's Tomb
- There was no blood moon on April 8, 2011. Even if we are to assume that the lunar calendar is different in this universe, the blood moon happens just eight days after a new moon. This is impossible.
- It's stated that Dionysus was sent back to Camp Half-Blood to complete his 100 years, however, it should be 50 years, as he was pardoned 50 years for his bravery during the Second Titanomachy.
- It's possible that Zeus forgot about his bravery or simply went back on his word.
- On the US cover, Apollo's zombie lines are missing.
- In Chapter 12, Larry says he is from the Third Cohort, and is shown to be leading it during the Battle of San Francisco Bay, but according to The Son of Neptune, he leads the Second Cohort.
- He could have been moved to a different cohort in between the books.
- In Chapter 18, Apollo refers to Hemithea as "Emma" instead of her nickname "Emmie".
- Also in Chapter 18, Pranjal refers to his father as Asclepius instead of his Roman name, Aesculapius.
- Reyna, while talking about her encounter with Aphrodite in Chapter 24, says, "I doubt there's anyone at Camp Jupiter who doesn't know what she told in me Charleston." The words "in" and "me" should be switched.
- Despite the Sibylline instructions, no Iris Message is used in the single-deity summoning ritual.
- It may have just not been described as the entire ritual wasn't described.
- Frank mentions the "Wakanda Thing" when discussing funneling, telling Terminus to open the barriers in one place. Infinity War came out in 2018, way ahead of the timeline.
- Don should have died instantly from the Greek Fire, but somehow survives from his burns for at least 12 hours.
- In Chapter 40, it recognizes the death of Dakota, "long-time centurion of the 5th legion," when it should have said 5th cohort.
- Reyna says "Calypso's Island" in Chapter 41, but she should have said "Circe's Island".
- After the battle, Hazel is promoted to praetor, and she promotes Lavinia to take her place, leaving the Fifth Cohort without a centurion. However, Dakota's death left the Fifth Cohort without its other centurion, but this is never addressed, and no one is known to have been promoted to co-centurion.
The Tower of Nero
- Will mentions that the first stanza of their terza rima prophecy came from Tyson's armpit, but it actually came from his chest, above his spleen. It was the single-deity summoning ritual that was on Tyson's armpit.
- Apollo mentions that when Meg sprinkled seeds into the sewer scum when they escaped from the tauri silvestres mushrooms popped out, however this isn't possible as mushroom reproduces from spores and not seeds.
Stand Alones
The Sun and the Star
- On page 148, Echidna says that echidnas are not hedgehogs, they are related to the anteater. While it is true that echidnas are not hedgehogs, they are not closely related to anteaters.[3] Echidnas make up the family Tachyglossidae in the order Monotremata,[3] while true anteaters are in the order Pilosa.[4] It’s likely Rick Riordan made this mistake as echidnas are also called spiny anteaters.
- In chapter 42, Nico says "My mother is Bianca di Angelo..." That is incorrect. Nico's mother is called Maria di Angelo. Bianca is Nico's sister.
- Once again, Nico is shown to have his memories with no explanation for their return despite the River Lethe erasing them.
- However, it is possible that the effects of the Lethe are temporary on the living.
- During Nico's first time in Tartarus, he encounters Nyx and her son, Hypnos. It is suggested that Hypnos fled down there after being responsible for the sleep spell that put Manhattan to sleep during The Last Olympian. However, in The Last Olympian, it showed that his son Morpheus was responsible for putting Grover and all the mortals to sleep. We don't know what side Hypnos was on during the Second Titan War, so it is not inconceivable that Morpheus was working in tandem with his father. It is unlikely however, given that Hypnos could have done it on his own given that he was powerful enough to put Zeus to sleep for a little while.
- After completing the quest, Hades allows Nico to speak with him mother and sister, who are both said to be in Elysium. However Bianca chose to be reborn over a year before the events of the book.
- They are also stated to only be a piece of their essence rather than their full spirits.