Mistakes in the Two Series!

No matter how hard an author tries, there will still be mistakes in their books if it is a series.  These mistakes include character flaws and continuity errors.  Some of the mistakes in the books are discussed by Rick Riordan, himself, via Twitter, or his Blog, but most are not explained directly in the books.  Here I will list the mistakes I have found, and the ones I have found by reading other people's interpretations.  Please note that I may not, and probably will not, catch every mistake.  If you know of one not listed here, please feel free to email me, and I will be sure to credit you.

Red = Fixed via Blog or Twitter
Pink = Sort of fixed in the book
Blue = Never fixed

The Lightning Thief

• It is stated that the gods move to where Western Civilization is the strongest, and that is why they are currently in the USA.  Also, many historical figures are named, such as George Washington. America did not become a world power until many years later than George Washington (almost 100).
• Even if the gods had moved to America in the 1700's, the current location of Olympus (The Empire State Building) had not existed yet (it was completed in 1931)
• It is mentioned in The Last Olympian, however, that there are foreign demigods, meaning that demigods aren't always born in the countries in which the gods live
• The American cover of the novel features Percy in the Long Island Sound holding Riptide and the Minotaur's horn.  This scene never occurred in the book.

The Sea of Monsters

• Thalia appears in Percy's dream having green eyes. However, Thalia is shown to have blue eyes when she appears further in the story.
• This could simply be due to the fact it was a dream
• Annabeth tells Percy she knows parts of the Great Prophecy.  However, later in the story, she mentions knowing the Great Prophecy in its entirety.
• While saving Blackjack from the Princess Andromeda, Percy calls Blackjack a mare (female horse). However, Blackjack is male in all other appearances.
• During a Q&A on his Twitter account, Rick Riordan stated Percy didn't know Blackjack was a male at the time

The Titan's Curse

• Hades is not at Olympus during the Winter Solstice even though this is the one time he is allowed to, and has to attend

The Battle of the Labyrinth

• Percy mentioned that three years ago, when he started camp, there was more than a hundred campers.  However, Percy started camp just two years ago.
• Chiron had called a war council to meet at the sword arena before Annabeth's quest, in which all head counselors were to attend.  However, the head counselors of Demeter and Dionysus did not attend.
• The American cover of the novel features Percy standing by Kronos' Coffin.  However, in the book he couldn't be seen there, for he was wearing Annabeth's Yankees Cap, and was invisible.

The Last Olympian

• Silena Beauregard's hair and eye color change from that mentioned in The Demigod Files.
• It is possible that since Silena is a daughter of Aphrodite, her appearance changes naturally.
• It is revealed that after Zeus had tried to kill Nico and Bianca, Hades placed them in the Lotus Hotel and Casino.  However, they were placed inside when they were infants, so it is unknown how they grew to the ages they are in The Titan's Curse.
• It is possible that they were not placed directly in the Lotus Hotel and Casino.  This fact is backed up by Bianca seeming to have some memory of living in Washington D.C. in the past.

The Lost Hero

• While Jason is given a tour of Camp Half-Blood, he is told that new cabins were built last year.  However, The Lost Hero takes place only four months after The Last Olympian, in the same year.
• While Jason is battling Porphyrion, he mentions being the leader of the First Legion. However, we later learn that Camp Jupiter is composed of the Twelfth Legion.
• This could be due to the fact that he had had his memories taken from him
• Rachel is said to be going to Clarion Ladies Academy in New Hampshire.  However, in The Last Olympian, it is stated that this school is in Connecticut 
• The American cover of the novel shows Piper still having Aphrodite's Blessing.  However, at this point in the book, it was almost fully gone.

The Son of Neptune

• Percy yells at Hera (Juno) for taking eight months of his life from him.  However, Percy was only missing for six months (December-June)
• Percy is being chased by Stethno and Euryale, the gorgon sisters of Medusa.  However, in The Lightning Thief, Medusa tells Percy that her sisters had faded.  Fading is the equivalent of permanently dying for immortals and monsters.

The Demigod Diaries

Leo Valdez and the Quest for Buford

• It is mentioned that Leo has been working on the Argo II for two months. However, this story takes place less than a week after 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 arrived at camp.
• Soon after the Argo II was forced to flee Camp Jupiter, Percy sees the sunset over a live feed of Camp Half-Blood.  However, at the time, it was only early afternoon in the summer, making it very unlikely for a sunset.
• Hazel mentions to Leo that she hadn't 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 eldest.  However, Otis and Ephialtes have been helping Arachne capture demigods for centuries.
• It is possible that Otis and Ephialtes never truly rose, as they had made their home under the surface of Rome.
• When Piper and Jason are talking to Bacchus, he mentions how he had fought alongside Heracles.  However, Heracles is Hercules' Greek name, and Bacchus is Roman.
• Percy mentions that he knew the Romans for weeks.  However, by this point, he had only known the Romans for about ten days, including the time he spent with Frank and Hazel on his quest.
• At one point, Leo sets his clothes partially on fire when he is woken up by a large ship.  However, Leo's clothes have been immune to fire at every other point in the series.
• Hercules warns Piper and Jason that he will kill them and their friends on the Argo II if they try to contact them.  However, later, when Piper thinks of a plan, she uses an Iris Message to contact them.
• It is possible that Hercules just didn't notice the message.
• Frank mentions in The Son of Neptune that the only Chinese character he knows is his family name.  However, 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 takes place only four years after the events in The Lightning Thief.

Well, that's all I've got!  Again if you have any more, or have a problem with any of mine, please feel free to either leave a comment, or email me at percyjacksonjunkers@gmail.com!

Thanks for Reading!