Percy describing the surreal and odd events that keep happening to him on every school trip, usually resulting in expulsion. Shooting a Revolutionary War cannon at the school bus and dropping the whole class from the catwalk into the shark tank are just two high points.
When Mrs. Dodds threatens him with a lot of pain, Percy thinks they figured out he cheated on his Tom Sawyer book project and might take away the grade. Or worse, make him actually read the book.
Also earlier he had mentioned he had never gotten higher than a C- in his life. That means he got no better than a C- on a report he printed online even though they never knew that.
Mrs. Dodds's last threat: "Die, honey!"
"I wasn't sure where the Latin came from, but I'm pretty sure it meant 'eat my pants'."
Percy:Braccas meas vescimini!
Percy yells at the Minotaur: "Hey! ...Hey, stupid! Ground beef!"
Soon after the Minotaur fight when Percy comes to and meets Annabeth, he thinks she will remark on his beating the Minotaur, but instead what she says is that Percy drools while sleeping.
As Grover puts about Hera and her lack of Demigod kids...
Hera doesn't run around having affairs with mortals. That is her husband's job.
Not to mention that Percy asks why Hera and Artemis have a cabin in the first place, neither having (demigod) children.
Chiron's imitation of the adult and serious arguments Poseidon and Zeus have on a regular basis. "We all know you were mom's favourite!" "Celestial phenomena are so much cooler than marine ones!"
Percy makes humorous monologues even during the darker parts of the book.
Even before they meet him, Percy meshes Fridge Horror and Mood Whiplash seamlessly at the top of the arch. He asks how they can know Hades isn't in the same room wearing his Helmet of Obscurity, which allows him to be invisible inaudible and intangible. Grover and Annabeth admit they in fact cannot know that. Percy's reaction? Asking them if they want some Oreos.
Talking about Hades, when the heroes finally confront him, he is hilariously pissed that people would think he was the one behind the theft. Percy suggests he would want a new war to get more subjects... and Hades angrily replies that, with all the people dying everyday (especially with the WWI, WWII, Korean War, Persian Gulf War, the War on Terror), he already has more subjects than he would want to or could possibly finance and organize, and throws in some more complaints about security ghouls, traffic problems, and overtime for his staff.
"Do you have any idea how many new subdivisions I had to set up just in the twentieth century?"
In hindsight, his similar complaints about his Underworld expenses. His Roman form is Pluto, who lords over all riches underneath the earth (though Hades in this book claims ownership of all the gems and precious metals too) - apparently he can't help himself too well.
As Hades rants, Percy out of nowhere relays Charon's request for a raise to him, which then leads to Hades to seamlessly segue into another rant about his employees' complaints.
Percy deliberately ticking off the gods by mailing Medusa's head to Mount Olympus in The Lightning Thief. The "With Best Wishes, Percy Jackon" bit is what really sells it.
Grover: They're not going to like that. They'll think you're impertinent. [After inserting a few drachmas into the package, it promptly disappears with a pop]
Percy: I am impertinent.
The package actually reappears, now with Percy's address in NY and "return to sender" added in a man's handwriting- the implication being that it's from Poseidon.
Percy "tearfully" rewarding the people of Los Angeles with free appliances from Smelly Gabe's store at the end of book one. He even provided the telephone number.
The scene where Grover tells Percy that he met a pink poodle named Gladiola who ran away and though he doesn't really want to rejoin his owners, he is willing to let Percy and the gang take him home for a $200 reward because that'll help Grover. And then they tell Percy to say hello to it.
Percy: I'm not saying hello to a pink poodle, forget it.
Annabeth: Percy, I said hello to the poodle. You say hello to the poodle.
Percy:(says hello to the poodle).
Poseidon's summation of his brother after Zeus threatens to kill Percy if he ever dares set foot in his domain (i.e., travels by airplane or anything similar) and Zeus... flashy exit: "He would be an exceptional god of theatre."
Earlier, when Percy just arrives with the master bolt but hasn't taken it out yet...
Zeus: I should have shot you down with a lightning while you were on the plane!
Sally's letter to Percy at the end. Gabe has mysteriously vanished and the police is searching for him but Sally has a feeling they won't have much success finding him... in the meantime, she sold a statue for a lot of money and got glowing reviews for its hyperrealism, so she has put down the advance payment for a new apartment, but she calms Percy saying she won't be putting sculpture on her new hobby list.
The last we see of Sally, she stares at Gabe in Tranquil Fury... then her expression changes into one as if she's wondering how Gabe would look as a statue in the garden.
Percy’s dream after defeating the Minotaur and passing out has him viewing Annabeth. He sings in awe about how he’s never seen someone so beautiful as the music swells triumphantly...only to get cut off by Annabeth’s deadpan reaction. “You drool in your sleep.”
The Sea of Monsters:
Percy's rivalry with Tantalus:
Percy's narration: This was so completely unfair that I told Tantalus to go chase a donut, which didn't help his mood.
Also, Percy finding out about Tantalus's punishmentnote He's unable to eat or drink anything initially:
Percy: You must have done something really bad to deserve that. [Beat] What was it? note Killing his own son and serving him up as stew or soup is what.
When Polyphemus becomes engaged to Grover, who's playing along as a girl. Voice and all. 'Nuff said.
"The bridge fell away into the chasm, and the Cyclops howled… with delight, because he was standing right next to us."
After Annabeth arrives to rescue Percy from a bunch of giant cannibals:
The Canadian thing also shows up in The Heroes of Olympus, where it's revealed that Laistrygonian Giants really are Canadian - they show up in Vancouver to attack Frank Zhang's house. And then Percy calls them "Canadians", much to the offence of genuine-Canadian Frank standing right there.
After Percy and Annabeth narrowly survive being eaten by the Sirens, Annabeth shares what she learned:
Annabeth: My fatal flaw. That's what the Sirens showed me. My fatal flaw is hubris. Percy: That brown stuff they spread on veggie sandwiches? Annabeth: No, Seaweed Brain. That's hummus. Hubris is worse. Percy: What could be worse than hummus?
Percy gets turned into a hamster.
In the film version, Dionysus has this to say about the curse he got for ticking off Zeus, which is that any wine he tries to drink turns to water.
Dionysus: You know, the Christians have a guy who can do this trick in reverse. *beat* Now that's a god.
The best part is that he looks up when he says the last bit, as if making absolutely sure that Zeus can hear him.
Hermes mentioning the TV show Heracles Busts Heads. Made even funnier in the movie because Nathan Fillion plays Hermes, and he mentions that the show was 'cancelled before its time.'
When Percy sees the Princess Andromeda ship, he remembers the myth about how she was chained to a rock by her parents as a sacrifice to a sea monster. He guesses that it was because she got too many F's on her report card.
Although it's in the middle of a serious scene, Annabeth's description of hubris is pretty funny. "Don't you ever feel like, what if the world really is messed up? What if we could do it all over again from scratch? No more war. Nobody homeless. No more summer reading homework."
The Titan's Curse:
Sally is so nervous when driving Percy and Annabeth to the school for their mission that she rambles on about Percy as a baby and the poor kid is willing to fall into the snow to cover his shame.
The book starts with Thalia, Percy and Annabeth on a mission at a school disco. Thalia's reaction? Asking who the hell picked the music and changing it to Green Day.
Nico asking Percy a million questions and he's so fed up that he considers wrapping Nico up into a meat filled sleeping bag and tossing him to the Hunter's wolves.
One of Nico's questions was whether or not Percy could surf on water. In the movie adaptation of Sea of Monsters, Percy apparently can.
Thalia's reactions to meeting Apollo for the first time, followed by Percy's confusion.
Thalia: Wow, Apollo is hot. Percy: Of course, he's the god of the sun. Thalia: (grumbling) That's not what I meant...
Even Nico is oogling Apollo. This becomes a little funnier in Blood of Olympus when he recounts this thought after seeing Will, a son of Apollo and wonders why he was thinking of that of all times.
Apollo after Thalia crashes his sun chariot. "Well! You were right, my dear. You had everything under control. Now, let's go see if we boiled anyone important, shall we?"
The entire scene is funny in itself. Thalia is trying to drive the Sun Chariot (which Apollo normally drives as a sports car, but turned into a shuttle bus to fit everyone) across the sky to Camp Half-Blood while everyone else is yelling directions at her and telling her to slow down and loosen up. Could also count as a Crowning Moment of Awesome considering she was able to drive a flying shuttle bus all the way from Maine to Long Island without completely trashing it... while being terrifiedof heights.
Percy also makes note of the Hunters who sat in the far back of the bus to get away "from us males".
Grover taking Nico to watch the orientation, and they somehow managed to make it PG, to the boy's delight.
As they prepare for a game of capture the flag, Nico is excitedly bouncing around and asks Percy about the rules. Percy looks at the clearly oversized armor on the demigod and wonders in embarrassment if he looked that stupid when he was younger.
Mr. Paul Blowfish, anyone?
Turns up later when Poseidon, entirely serene, thinks that it's actually his name. When Paul slightly testily corrects him, Poseidon says, slightly absently, "Pity, I quite like blowfish."
Poor, poor Zoe... "Lord Apollo has been going through this haiku phase ever since he went to Japan. 'Tis not as bad as the time he visited Limerick. If I'd had to hear one more poem that started with 'There once was a goddess from Sparta'..."
Thalia constantly correcting Zoe's thee-s and thou-s into you-s.
The scene at Hoover Dam. Especially since Zoe's lack of knowledge of modern English kept her from getting the dam joke.
Zoe: "Let us find the dam snack bar. We should eat while we can."
Percy wondering how Kronos fits in to the disappearance of Artemis:
Percy's narration: "Kronos could influence people with dreams and trick them, but I didn't see how he could physically overcome Artemis if he was still like a pile of evil bark mulch."
The General's first attempt to grow an army of soldiers with dragon teeth. His minion confuses the teeth with sabercat teeth, which ends up growing adorable kitties. The General is not amused. Made even better by the fact that this is after he delivers an evil speech about his most invincible army, right before the kitties appear. One of these cats reappears in The House Of Hades.
The Battle of the Labyrinth:
During orientation at Goode High School, the marching band is playing a fight song that sounds like "someone beating a bag of cats with a metal baseball bat".
Annabeth happens to know the old trick of keeping to the left hand wall. She makes the mistake of saying so out loud, and the Labyrinth promptly changes to a circular room with eight identical doors.
Tyson: Left walls are mean.
Also happening with Annabeth in that same room, when she gets ticked off by Hera's 'help', and all the remaining food disappears before Tyson can finish.
Annabeth:[stamps foot in frustration] What sort of help was that?! "Here, have a sandwich. Make a wish. Oops! I can't help you! Poof!"
When Rachel kisses Percy on the cheek, Beckendorf says, "I'm guessing you don't want me to mention that little scene to Annabeth?"
The scene where Percy and Annabeth witness the Ares and Apollo cabins fighting over a chariot they seized in Philadelphia. They see an angry Ares camper run by cursing in rhyme! "Curse me, eh? I'll make you pay / I don't wanna rhyme all day!" Annabeth groans, complaining that it took a full week for the rhyming couplets to wear off the last time Apollo cursed a cabin.
Moments later, Percy notes his admiration of an Ares camper's ability to viciously cuss out a Hermes camper in perfect rhyme.
Selena is too depressed over Beckendorf's death that she refuses to eat the box of chocolates her father had sent, claiming it tasted like cardboard. Percy takes a chocolate, saying he had nothing against cardboard.
At the end Percy and his friends are victorious, Olympus is saved, the gods are doling out rewards, Tyson is promoted to be general of the Cyclopes, and is granted any weapon he desires, creating a Mundane Made Awesome moment.
Zeus: what kind of weapon would you like? A sword? An axe?
The Party Ponies. They're basically a fraternity of hyper-active centaurs. "HAWAII OWNS YOUR FACES!", anyone?
Oh, and the arrow that's fitted with a boxing glove. Almost like a Get Smart device.
George's running gag of always wanting a rat and his and Martha's bantering. And what their names are. He seems to be too preoccupied on that.
Mrs. O'Leary the Hellhound. That is all.
Anytime Percy is jealous of Luke (particularly of Annabeth's feelings for him), Percy usually has something snarky to say.
Some of Percy's inner monologues are just hilarious. For example, "If you've never been charged by an enthusiastic Cyclops wearing a flowered apron and rubber cleaning gloves, I'm telling you, it'll wake you up quick."
Almost every character in the series says something funny, even when they do not mean it. Even Kronos has his moments.
The table of contents in every book is guaranteed to give at least a few laughs ("A God Buys Us Cheeseburgers", anyone?)
The title chapters have added hilarity due to It Makes Sense in Context. "I Scoop Poop" and "Nico Buys Happy Meals For The Dead" from the fourth book come to mind.
Heck, the hilarity starts with series's first chapter, "I Acidentally Vaporize My Pre-Algebra Teacher".
Most of the times a god shows up for a one-off scene, especially when they are referencing well known heroic fantasy tropes in a casual manner as if they are entirely the way the world should work. Aphrodite in particular springs to mind as being ridiculously funny, but Hermes has his moments also.
Some of the confirmed historical demigods can give you a hearty chuckle when you start to think about it.
George Washington was a son of Athena... which can give you the mental image of him screaming his head off at spiders as every Athena-child is terrified to dead of them.
Thomas Jefferson is confirmed as one of the judges in the Underworld... but then you remember Zeus and Hades had a deal saying that all judges MUST be Zeus' children, which in a Black Comedy way means Thomas Jefferson had to contend with the mother of all wicked stepmothers herself, Hera.