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!!For the main series:
* {{Anvilicious}}: Dav will never let you forget that ''kids need imagination and fun in their lives'' and it plays as much of a role in their future as having an education.
* DesignatedHero: George and Harold have a tendency to slip into this with some of their pranks. In the first book, they cause enough disruption at a school football game to get the school to forfeit it, and subsequently ruin everyone else's day, and Captain Underpants is later created as a result of their attempt to avoid being punished for this. In the second book, they sabotage the school's Invention Convention out of spite, due to them not being allowed to attend following the prank they pulled last year. These only apply to the first five books, however. As the books continue, we see more outside threats not by them or by returning villains
* EnsembleDarkhorse: The cheerleaders from the first book due to their TheWoobie status and how they reappeared in the ninth book and one of them got a name.
* FridgeBrilliance: Book 12 received a lot of praise for revealing that [[spoiler: Future Harold]] is gay without making a big deal about it. [[spoiler: Future George meanwhile has a wife that is only ever referred to as "Mrs. Beard". "Beard" of course is a term referring to a woman that has married a gay man.]] [[AlternateCharacterInterpretation Have fun with that, fanfic writers!]]
** Dav later confirmed that said wife was actually named "Lisa."
* FridgeHorror: A few with the 3-D Hypno-Ring:
** For starters, it's a ''consumer-level MindControlDevice''. All you have to do is trick or force the poor victim into looking at it for a few seconds and snap. JustThinkOfThePotential...
** In ''Wrath of the Wicked Wedgie Woman'', it's revealed that the ring was recalled because for unknown reasons, it worked the opposite of its wielder's intentions on women. UnfortunateImplications aside, this might seem like jumping the gun to younger readers, but George and Harold used it on their already-SadistTeacher and [[GoneHorriblyWrong look what happened]]. Now, what about all the other kids who had one? Chances are, the first thing a lot of them would use it on is their parents, who they typically have a [[AdultsAreUseless very low opinion of]]. All of a sudden, there'd be an outbreak of [[AbusiveParents Abusive Mothers]] all across the country because the kids demand that their every whim be catered to. That wouldn't go unnoticed and would be a pretty damn good reason to recall them.
* GrowingTheBeard: The series started out as just simple harmless children's entertainment and little else. However, by the 4th and 5th books, Dav's commentary and messages become clear to more observant readers, with just enough subtlety to keep smaller readers entertained but still encouraged.
* HeartwarmingInHindsight: In the library where the boys traveled to a different dimension, one of the books parodies the controversial children's book, ''Heather Has Two Mommies''. Then in the 12th book, [[spoiler:Harold marries a man with two children.]]
* HilariousInHindsight: In the original [[foldercontrol]]

[[folder: EPIC NOVEL ]]
, Mr. Krupp talks of a NoodleIncident involving George and Harold riggin the school intercom to play Music/WeirdAlYankovic music. Years later, he composed and performed the movie's theme song.
* ItWasHisSled: Thanks to the internet, there's no hiding the fact that [[spoiler:Harold is gay in the 12th book]].
* JerkassWoobie: Professor Poopypants. He just wanted people to stop laughing at his name, though George and Harold point out that he could have simply changed it rather than forcing everyone else to change their name into something ridiculous.
* LGBTFanbase: A curious case, as the LGBT people who are fans of the series are primarily made up of people who actually read the books as children, ''before'' realizing they were LGBT, but have since flocked back to the series in recent years, both out of nostalgia and after the reveal that [[spoiler:Harold turns out to be gay]]. It helps that the long hiatus gave a lot of the early readers time to grow up and "grow out" of the books, before said reveal revived their interest.
* MagnificentBastard: A heroic example. [[spoiler: Kindergardener George and Harold come up with a BatmanGambit to enact revenge on the bullies.]]
* {{Moe}}: Kindergardener George and Harold.
* MemeticMutation: The [[http://knowyourmeme.com/memes/melvin-comicsfcking-melvin Fucking Melvin]] Webcomic/RageComics, which are likely based on Melvin Sneedly.
** The [[https://www.youtube.com/watch?v=zV8v6d-MLL0 song to tie in with the books]] was one of many affected by the "[[Series/LazyTown We Are Number One]]" remix treatment, but this was only up until the movie came out.
* NauseaFuel: Inevitable in ToiletHumour-themed series, but the Bionic Booger Boy gets special mention. His descriptive introduction is cut off when George yells at the narrator for making everyone sick.
* NightmareFuel: The giant man-eating dandelion in Book 3.
** [[spoiler: The BadFuture created by Tippy Tinkletrousers. On top of this disaster-layer cake, we also saw gigantic zombie nerd-versions of George and Harold. Also from this section of the book, Tippy is crushed, blood and all. Doubles as a TearJerker.]]
** The children affected by the Rid-O-Kid 2000.
* OlderThanTheyThink: Dav Pilkey's first drawing of Captain Underpants dates all the way back to the very events that inspired him in second grade. He drew the character in class after his teacher outright said that underwear isn't funny. When he was sitting in the hallway as punishment, he proceeded to draw ''an entire comic book'' of the character! Sadly, both of these were torn up in his face by his unamused teacher.
* PeripheryDemographic: The books have a lot of teenaged and even adult fans -- both people who read the books for the first time as kids and simply never stopped enjoying them, or people who read them ''to'' kids, and found that they could enjoy the more clever, subtle humor and social commentary while the kids enjoyed the superheroes and toilet jokes.
* TheScrappy: '''Mr. Meaner'''. A lot of fans didn't like him before, but after Book 12, they quickly grew to ''despise'' him.
* {{Squick}}:
** A grown man runs around in his underwear with two ten-year-old boys. Okay, ItMakesSenseInContext, but still...
** Taken UpToEleven in (appropriately enough) Book 11, where the boys convince all of the teachers and faculty that they're in a dream. This prompts the grownups to release their inhibitions by performing all sorts of shenanigans ''in their underwear.'' And yes, Dav Pilkey illustrates this repeatedly...
** When Crackers's eggs hatch and the creatures inside are half-hamster. Harold imagines different scenarios that could lead to the possibility of [[HotSkittyOnWailordAction a bionic hamster mating with a prehistoric reptile]], but George can only say "EEWWWWWWWWWW!"
* StrawmanHasAPoint: While the school faculty and Melvin are deliberately written to be [[HateSink unlikable]] and get kicks of making the students miserable. Their animosity towards George and Harold does serve good points, as mentioned above and below. The boys often caused unprovoked trouble to not only to the faculty and Melvin, but to their fellow students as well.
* UnintentionallyUnsympathetic: George and Harold, due to being [[DesignatedHero Designated Heroes]], ''especially'' in the first five books. To wit:
** In the first book, they ruin a football game ForTheEvulz, and when Mr. Krupp catches them doing it, he lists off some of their other major offenses during his EvilGloating (putting bits of dissected frogs in jello at a parent-teacher banquet, making it snow in the cafeteria, rigging the intercoms to play the music of Music/WeirdAlYankovic at full blast for six hours), which makes their subsequent punishment seem more like LaserGuidedKarma since they went out of their way to deserve it.
** In the second book, they ruin a science fair out of spite because they were (rightly) banned from it due to a prank they pulled the previous year, making their punishment well-deserved.
** In the third book, they sadistically torment the science teacher simply because they find his class boring. They also pulled many stunts towards the lunch ladies (the only faculty members who ''aren't'' shown to be [[JerkAss jerks]]) such as changing their signs, playing with the lunch trays, making fun of their cooking, and creating comic books about them.
* WhatDoYouMeanItsNotPolitical: The books are no stranger to criticizing how public schools treat neurodivergence, especially ADHD. Book 12 in particular makes a BlandNameProduct version of Ritalin the villain's mind control gas that suppresses creativity and individuality.
** The same book makes reference to the GOP hating people who are young and different from them. In this case, it stands for Grumpy Old People, but American readers will recognize the acronym as that of the Grand Old Party, AKA the Republican Party.
* TheWoobie: Kindergartner Harold. His dad's gone before the book starts, he's bullied on a daily basis, and it's all but stated he draws constantly because of everything that's happened to him. It's no wonder he's friends with George after the kid saves him.[[note]]Even sadder, this is all taken verbatim from Dav Pilky's actual childhood (save the DisappearedDad).[[/note]]
** Melvin could possibly count as a JerkassWoobie (at least before he TookALevelInJerkass from Book 7 onwards), as it is kind of implied in Book 6 that his parents care more about their scientific work than they do their own son. They didn't even seem to ''notice'' that he had become the Bionic Booger Boy until they saw his rampage on TV.
!!For the {{Spin Off}}s:
* EsotericHappyEnding: The ending of ''The Invasion of the Potty Snatchers''. Billy and Diaper Dog stop Rip Van Tinkle from destroying the city, but they never actually solve the lack of toilets problem, when the lack of toilets was the main conflict of the book in the first place. Despite this, the ending is still presented as a "happy" one.
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