History AdaptationInducedPlotHole / PercyJacksonAndTheOlympians

* Less of a plot hole, but more of a strange unaddressed issue happens in the movie due to Percy's group having different initial motivations. In the book, Percy was sent by Chiron to reclaim the stolen master bolt from the Underworld under the assumption that Hades stole it. In the movie, Chiron instead wants Percy to go to Olympus to convince Zeus of his innocence in person, but Percy bails on him in order to rescue his mother from the Underworld, having been given no reason to think the bolt is there since Hades actually demands it in exchange for Sally's release. But since the war of the gods will be apocalyptic and Percy ditched his best hope at preventing it, logically, [[DidntThinkThisThrough Percy's mother is doomed after the winter solstice deadline whether or not Percy's group rescues her from the Underworld,]] but neither Anabeth nor Grover ever point this out, even as they react with worry and haste to signs of the coming war in the news and lose several days to the Lotus Casino.

* Less of a plot hole, but more of a strange unadressed issue happens in the movie due to Percy's group having different initial motivations. In the book, Percy was sent by Chiron to reclaim the stolen master bolt from the Underworld under the assumption that Hades stole it. In the movie, Chiron instead wants Percy to go to Olympus to convince Zeus of his innocence in person, but Percy bails on him in order to rescue his mother from the Underworld, having been given no reason to think the bolt is there since Hades actually demands it in exchange for Sally's release. But since the war of the gods will be apocalyptic and Percy ditched his best hope at preventing it, logically, [[DidntThinkThisThrough Percy's mother is doomed after the winter solstice deadline whether or not Percy's group rescues her from the Underworld,]] but neither Anabeth nor Grover ever point this out, even as they react with worry and haste to signs of the coming war in the news and lose several days to the Lotus Casino.

* Rather than just having Percy come across the guy from the 70s on his own like in the book, the film Poseidon has warn him telepathically about being trapped inside the casino before he thinks to investigate anything. But Poseidon only does this ''after'' Percy and his friends have been inside the casino for five days, raising the question of why he waited so long when time was of such a crucial essence.

%%* In the books, nobody except Sally and the gods know who Percy's dad is. There's a whole process called Claiming where a god will reveal to their demigod child their true parentage, and it's considered an honor at Camp Half-Blood. When it's revealed that Percy's father is Poseidon, the event is news to just about everyone at Camp Half-Blood. The movies cut this whole thing out, and have the Camp know Percy's father ''before he even comes''. But if they all knew who he was ... why didn't they just take him to Camp Half-Blood as a kid? The baby Percy could have just been sent there in his youth, preventing him from facing his various childhood dangers. Not to mention they would have known the gods would blame him for stealing the book.
* The movie seems to forget what Percy and his friends are motivated by about halfway through the story, as the initial reason for their quest to the Underworld varies between the book and movie. In the book, Percy was sent by Chiron to reclaim the stolen master bolt from the Underworld, under the assumption that Hades stole it. In the movie, Chiron instead wants Percy to go to Olympus to convince Zeus of his innocence in person, but Percy bails on him in order to rescue his mother from the Underworld, having been given no reason to think the bolt is there since Hades actually demands it in exchange for Sally's release. However, this is seemingly forgotten about after the action at the Parthenon; after viewing a newscast about the bizarre weather Zeus and Poseidon's conflict is causing, the trio suddenly act as though getting to the Underworld before the war starts will preempt it from happening, ignoring the fact that that wasn't their goal at all in the adaptation and that they still have no idea where the master bolt is.

There’s a reason why everyone hates the movies.

** To start with, Luke provides a map to a set of pearls that Percy and his friends can use to escape the Underworld once they're inside, without which getting out is said to be impossible. The pearls turn out to work exactly as advertised; however, true to the book, Luke later admits it was never his intention for Percy to leave the Underworld alive, begging the question of why he gave him the map in the first place. In the book, the pearls were actually a gift to Percy from Poseidon via a third party, hence why Luke hadn't factored them into his plan.

* In the books, nobody except Sally and the gods know who Percy's dad is. There's a whole process called Claiming where a god will reveal to their demigod child their true parentage, and it's considered an honor at Camp Half-Blood. When it's revealed that Percy's father is Poseidon, the event is news to just about everyone at Camp Half-Blood. The movies cut this whole thing out, and have the Camp know Percy's father ''before he even comes''. But if they all knew who he was ... why didn't they just take him to Camp Half-Blood as a kid? The baby Percy could have just been sent there in his youth, preventing him from facing his various childhood dangers. Not to mention they would have known the gods would blame him for stealing the book.

* The movie keeps the second book's plot thread about Percy's frustration at being shut out and ignored by Poseidon. While it is out-of-character for the Poseidon of the movie, who was much more endeared to and supportive of Percy than he was in the book, the first movie also stated that the gods were explicitly forbidden to communicate with their children. With no indication that Zeus had revoked the law in between movies, there's no reason for Percy to be taking his father's silent treatment as a personal slight--even through telepathy, Poseidon only reached out to him in the first movie once the threat of war became apparent.

* The movie keeps the second book's plot thread about Percy's frustration at being shut out and ignored by Poseidon. While it is out-of-character for the Poseidon of the movie, who was much more endeared to and supportive of Percy than he was in the book, the first movie also stated that the gods were explicitly forbidden to communicate with their children. With no indication that Zeus had revoked the law in between movies, there's no reason for Percy to be taking his father's silent treatment as a personal slight.

* While it is more accurate to the book, Poseidon giving Percy the cold shoulder this time seems illogical given the less-aloof way their relationship was handled in the first movie, in which Poseidon provides aid to Percy several times and promises to stand by him no matter what. In the book, while he was grateful and proud of what Percy had done, he wouldn't become nearly as attached to him until much later in the series.

* The movie seems to forget what Percy and his friends are motivated by about halfway through the story, as the initial reason for their quest to the Underworld varies between the book and movie. In the book, Percy was sent by Chiron to reclaim the stolen master bolt from the Underworld, under the assumption that Hades stole it. In the movie, Chiron instead wants Percy to go to Olympus to convince Zeus of his innocence in person, but Percy bails on him in order to rescue his mother from the Underworld, having been given no reason to think the bolt is there since Hades actually demands it in exchange for Sally's release. However, this is seemingly forgotten about after the action at the Parthenon; after viewing a newscast about the bizarre weather Zeus and Poseidon's conflict is causing, the trio suddenly act as though getting to the Underoworld before the war starts will preempt it from happening, ignoring the fact that that wasn't their goal at all in the adaptation and that they still have no idea where the master bolt is.

* Rather than just having Percy come across the guy from the 70s on his own like in the book, in the film, Poseidon has to warn him telepathically about being trapped inside the casino before he thinks to investigate anything. But he still only does this ''after'' Percy has been inside the casino for five days, raising the question of why he waited so long when time was of such a crucial essence.

** Luke sending the bolt along with Percy in secret is an even bigger example. In the book, Luke stole the bolt from Zeus, but was soon apprehended by Ares, whom he managed to convince to help start the war by passing it onto Percy, who would deliver it to Hades in the Underworld. (Luke's plan actually involved the bolt being delivered to Kronos via a pair of winged shoes that were cursed, but the movie also leaves that subplot out.) In the movie, Luke had the bolt with him the entire time up until he hid it in Percy's shield; there's no reason why he didn't keep it for himself as he intended to in the book, seeing as a war between the gods would've been of a large enough scale without Hades having it. Kronos being reintroduced in the sequel only further widens this plot hole, as the master bolt would've been a powerful tool for him and Luke essentially bartered it away for nothing.

* The Lotus Casino is a holdover from the book that throws a wrench into the film's sequence of events. In the book, Percy was questing to recover Zeus's master bolt from the Underworld in order to return it before the summer solstice deadline, which is why the group's five-day stay in the casino was significant for wasting so much precious time. In the film's version of the story, the motivation is changed to rescuing Percy's mother from the Underworld; the missing bolt and the deadline aren't pertinent to the quest at all up until the end, meaning the casino setback should no longer be that significant. And yet the three heroes still act like it is, saying that they must hurry on to the Underworld despite being given no reason to think that Zeus's bolt is even there, to say nothing of the fact that they weren't looking for it.

* The Lotus Casino is a holdover from the book that throws a wrench into the film's sequence of events. In the book, Percy was questing to recover Zeus's master bolt from the Underworld in order to return it before the summer solstice deadline, which is why the group's five-day stay in the casino was significant for wasting so much precious time. In the film's version of the story, the motivation is changed to rescuing Percy's mother from the Underworld; the missing bolt and the deadline aren't pertinent to the quest at all up until the end, meaning the casino setback should no longer be that significant. And yet the three heroes still act like it is, saying that they must hurry on to the Underworld despite being given no reason to think that Zeus's bolt is even there.

* The film switches the driving force behind Percy's quest so that he's trying solely to rescue his mother from the Underworld rather than reclaim the bolt from Hades. With a few changes, this doesn't have a major effect on the story until you factor in the escape from the Lotus Casino. In the book, their five-day stay in the casino was significant because it left Percy with only two days to find the bolt and return it to Zeus. The film also tries to include this dilemma, despite it being completely broken by the fact that Percy was never looking for the bolt in the film's plotline; he was in this solely to save his mother and has no idea where the bolt is. So he and his friends stressing over their "deadline" is completely nonsensical, because they never had a deadline to begin with.
* Hades claims to have sent the Minotaur to capture Percy's mother, rather than the Minotaur attacking on his own accord and Hades seizing the opportunity to get a bargaining chip like in the book. This raises the question of why the Minotaur doesn't just leave after completing his mission.
* The gods are said to be forbidden to communicate with their children. Except Poseidon talks to Percy and Annabeth says her mother Athena talks to her, with no sign that either one has to do so on the down-low or faces any consequences for breaking the rules.

* The film also has Persephone in the Underworld at the time the heroes visit there, which is on the eve of the summer solstice when she should be in the world above, like she was in the book. Even stranger is that she acknowledges that she does have allotted time to spend away from the Underworld, but whether the allotment has changed since the time of the myths or Hades was somehow keeping her trapped there against her will isn't addressed.

* Rather than just having Percy come across the guy from the 70s on his own like in the book, in the film, Poseidon has to warn him telepathically about being trapped inside the casino before he thinks to investigate anything. But he still only does this ''after'' Percy has been inside the casino for five days, begging the question of why he waited so long when time was of such a crucial essence.

* Rather than just having Percy come across the guy from 1971 on his own like in the book, in the film, Poseidon has to warn him telepathically about being trapped inside the casino before he thinks to investigate anything. But he still only does this ''after'' Percy has been inside the casino for five days, begging the question of why he waited so long when time was of such a crucial essence.

* There’s also a change of a single word that ruins part of Percy’s conflict in the fifth book. The movie makes it “the evil soul” that the “cursed blade shall reap” when in the book, it was the “hero’s soul.” Percy spent a good part of the book worrying he would end up dying because of that line. Changing the word to “evil” completely negates all that. It also makes [[spoiler: Rachel’s appearance useless since she receives a message saying Percy isn’t the hero. At first it’s another internal conflict for him, but at the climax he comes to understand it’s relevant to the prophecy.]]

''Movie''
* [[PunctuatedForEmphasis Poseidon rising out of the water in the beginning of the movie. In front of a fisherman. Who clearly acknowledges his presence]]. Only two minutes in and the filmmakers already show their misunderstanding of source material, where it was made very explicit that The Mist prevents mortals from knowing about gods. This begs the question as to how the gods managed to hide their conflicts when they are portrayed as pretty antagonistic and confrontational to begin with.
* In the book, Ms. Dodds was Percy's math teacher and knew him for much longer than in the film. Here, she's his ''substitute'' English teacher and already knows his name. [[spoiler: One could argue that she was disguised as a Fury and already knew Percy's name, but he didn't know that, so this just makes her look dumb]].
* Percy killing [[spoiler:the Minotaur]] with its own horn. While he did the same thing in the book, it was only because he didn't have his sword, which he had in the film.
* Percy's identity of being the son of Poseidon. It's treating like nothing in the film, but was a big deal in the book. However, that reason was AdaptedOut. The movie {{Hand Wave}}s it as it simply being rare for Zeus ([[ReallyGetsAround if you buy that]]), Poseidon, and Hades to have children but Chiron still has no reaction to what he just described as out of the ordinary.
* For some reason, Sally knew how to use the fuse box to the elevator to Olympus.
* Persephone was supposed to be with Demeter during summertime.[[note]]In the book, Percy himself wishes it wasn't summer so she would be there, because she is known to be able to calm Hades down.[[/note]] She even acknowledges such a fact.
* Hades never wanted to be king of the gods. [[spoiler: This was officially acknowledged in ''The Last Olympian'']], so he would've looked like a hypocrite in that movie.
* Luke says he never met his father, even though in the book, Annabeth was with him when he saw his father, so he's just lying through his teeth.
* The movie doesn't explain the book's concept of monsters coming back to life after a few years, leaving fans wondering why Medusa is still live when she was supposed to have been killed by Perseus.
''Musical''
* Like in the film, Percy wears the winged shoes, even though he was on Zeus's hit list at the time ''[[FromBadToWorse and]]'' is a son of Poseidon, so is therefore not allowed in the sky, so any form of aviation would be dangerous for him.

* Tyson questioning how the Colchis bull got inside the camp when he should be questioning how he himself got in. It made sense in the book because Annabeth let him in.
* Bringing in and defeating [[spoiler: Kronos]] in this movie. We can see how easy it was for Percy to take him down, so there's no point in bringing him back later. What makes it worse is that he swallows Luke, and I doubt he’d be willing to allow the Titan to possess him.
** Adding more to that, within the movie itself, it was stated that it took the combined powers of Zeus, Poseidon, and Hades to kill Kronos, but Percy is able to defeat him on his own.
*** MORE on that, In the fifth book, it is revealed [[spoiler: that Annabeth's knife was the cursed blade, not Percy's sword, which feels like an AssPull in of itself]]. It just comes as a rushed explanation to just rush the climax and possibly end the films here, but they still hint at getting a sequel before the end credits, the filmmakers clearly didn't make up their minds.
*** There’s also a change of a single word that ruins part of Percy’s conflict in the fifth book. The movie makes it “the evil soul” that the “cursed blade shall reap” when in the book, it was the “hero’s soul.” Percy spent a good part of the book worrying he would end up dying because of that line. Changing the word to “evil” completely negates all that. It also makes [[spoiler: Rachel’s appearance useless since she receives a message saying Percy isn’t the hero. At first it’s another internal conflict for him, but at the climax he comes to understand it’s relevant to the prophecy.]]
* Spoiling [[spoiler: Silena's role as the spy and bringing in Ethan Nakamura]] too early.
** The former would've been a plot twist in ''The Last Olympian'', so this is a major case of ForegoneConclusion.
* The [[spoiler:Party Ponies and Cyclopes]] help out in the Battle of Manhattan in ''The Last Olympian''. They would just appear out of nowhere in that movie, had it ever been made.
* Blackjack was removed, which is confusing because he becomes [[spoiler: Percy's companion in the last three books]].
* Grover's quest to find Pan was dropped entirely. This could be fixed (if the films had continued) by introducing it in ''The Titan's Curse'' or have an AssPull in ''The Battle of the Labyrinth''.
* Because the first movie didn't mention the Mist, this film had to rush in an explanation. It is introduced as a spray that is very rare to come across, but is later shown to work like how it is described in the book.

* Persephone was supposed to be with Demeter during summertime. She even acknowledges such a fact.

* [[PunctuatedForEmphasis Poseidon rising out of the water in the beginning of the movie. In front of a fisherman. Who clearly acknowledges his presence]]. Only two minutes in and the filmmakers already show their misunderstanding of source material, where it was made very explicit that The Mist prevents mortals from knowing about gods.

* Percy's identity of being the son of Poseidon. It's treating like nothing in the film, but was a big deal in the book. However, that reason was AdaptedOut.