* {{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. And in exchange for fixing all the damage done by the villains, they have Mr. Krupp cancel their punishment and let them run the school for the day, during which they sell a lot of the staff's furniture to pay for the party they throw for all of the students. Granted, they do try and stop the villains in every book, but the fact that many of them (the Talking Toilets, Poopypants, Wedgie Woman) appear as a result of George and Harold's actions doesn't help their case.
** Granted, there were unordinary circumstances. Poopypants/Tinkletrousers was eventually going to crack and the fact it happened at Jerome Horwitz was just a matter of chance. With Wedgie Woman, they were unaware of the fact that the Hypno-Ring has reverse effects on women. Also, the villains of the 3rd book, the aliens, was completely unrelated to them at all.
** These only apply to the first five books. As the books continue, we see more outside threats not by them or by returning villains (the latest book bringing back the [=TurboToliet=] 2000.)
* 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!]]
* 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.]]
* 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.
* 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.
* 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.
* {{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!"
* 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 loud music), 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. Then they pull a nasty prank on the lunch ladies (the only faculty members who ''aren't'' shown to be [[JerkAss jerks]]) that covers the entire school in slime for ''no reason whatsoever'', and as they are complaining to the principal, the lunch ladies list off the boys' other unprovoked offenses before resigning from their positions in disgust.
*** To be fair on the slime case that caused the lunch ladies to quit, George and Harold only intended to make it a small prank. The lunch ladies were the ones who decided to multiply the recipe by 1000, causing the slime incident. Never mind the [[FailedASpotCheck spot check they failed]] by not realizing what happens when you mix vinegar and baking soda, something taught in Fourth Grade the very same day.
** The fourth book makes it a bit more complicated. While Professor Poopypants was going to crack at some point anyway, making an offensive comic book about him was just plain rude. In fairness, George and Harold do admit at the end of the book that [[MyGodWhatHaveIDone they were wrong to make fun of him]]. Also, they were not the only ones that made fun of him.
** In the fifth book, they trick their homeroom teacher and principal into almost getting married. Sure, Ms. Ribble is a SadistTeacher, but considering the magnitude of this action, her decision to simply have them flunk the 4th Grade comes off as an ''extremely'' lenient punishment (especially since their grades aren't all that good to begin with), yet they have [[EntitledBastard the nerve]] to [[NeverMyFault feel sorry for themselves]].
*** To be fair on that last one, the whole situation could've been avoided if ''either'' Ms. Ribble or Mr. Krupp owned up to the fact that they didn't want to be married to each other some time ''before'' the actual wedding. George and Harold had nothing to do with the both of them failing to do that.
*** On the flip-side, it should be noted that Mr. Krupp ''did'' try to explain that it was all a trick, but was so shocked by the magnanimity of it that he was rendered temporarily brain-dead, speaking in stunned mumbles up until Ms. Ribble's loud rejection snapped him out of it. Ms. Ribble, on the other hand, has no excuse.
* 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.
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