History WesternAnimation / CaptainUnderpantsTheFirstEpicMovie

* RedOniBlueOni: Even though they’re technically the same person, Mr. Krupp and Captain Underpants certainly count, with Captain being the passionate, energetic, childlike, and optimistic Red to Mr. Krupp’s pessimistic, controlling, and authoritative Blue.
** George is the bold, leader-ly Red to Harold’s calmer, more sensitive Blue.

** Principal Krupp has also become a nicer guy, or at least a person who went from mean ForTheEvulz to one who was mean because he was lonely.

* BrickJoke: In the Flip-O-Rama segment, the last thing shown of what's happening to Captain Underpants is Professor Poopypants banging him around like a paddleball. Once we return to the real world, that's exactly what Professor Poopypants is shown doing.

* OffTheRails: InUniverse, when Harold goes into his fears about what would happen should Krupp succeed at putting them in different classes, he soon derails into describing a RobotWar. [[JustifiedTrope Justified]] by Harold after George points it out by noting that there's a reason George is the one responsible for writing their comics.

* SequelHook: A minor one, [[spoiler:after Professor Poopypants is shrunk, he successfully escapes riding on a bee. Meaning if a sequel is ever made, he'll most likely return. Also, the Talking Toilets make an appearance at the end.]] The film of course ends with Harold iconic "HereWeGoAgain"

* HereWeGoAgain: [[spoiler:Just when it looks like everything has calmed down, an army of talking toilets start attacking, and Mr. Krupp accidentally triggers his Captain Underpants persona, which was seemingly destroyed along with the hypno-ring. Heck, Harold even says it word-for-word! It's a ''Captain Underpants'' movie, [[OnceAnEpisode how else was it supposed to end]]?]]

* TeamMemberInTheAdapation: Melvin and Professor Poopypants were both major villains, but they never had any connection in the books. Here, they work together.

* AdultsAreUseless: None of the school's staff besides Ms. Anthrope notices Poopypants' attack on the school. Averted when the police show up after the attack.

* DidIJustSayThatOutLoud: At the end of Prof. Poopypants' flashback, most of the students who were just laughing at the Captain Underpants comic a moment ago have been left in stunned silence. This causes Poopypants to ask "...how much of that was out loud?"

* IdenticalTwinIDTag: Even when Captain Underpants is fully disguised in clothes, he can still be told apart from the regular Mr. Krupp because CU always wears his toupee lopsided.

* NiceJobFixingItVillain: [[spoiler:Professor Poopypants does this ''twice''. The first time was when he had the Turbo Toilet 2000 "eat" Captain Underpants. In doing so, he exposed CU to the pretty much radioactive leftovers from the school cafeteria, and it results in him getting ''real'' superpowers. The second time is when he's [[NearVillainVictory seemingly won after erasing George and Harold's sense of humor]]. He mentions the planet Uranus, which triggers the memory of how George and Harold first met, and gets them laughing again.]]

* UranusIsShowing: In a flashback, we see that snickering together at the word "Uranus" is the basis of George and Harold's ''entire friendship''. [[spoiler:It's also what helps them resist Prof. Poopypants' anti-humor ray at the end]].

* DidntThinkThisThrough: Most of the first half of the movie involves George and Harold dealing with the aftermath of making their principal think he's a superhero, mainly having to keep him out of trouble and having to keep him from getting wet.

** The story of how George and Harold met in kindergarten is briefly touched on, complete with the same designs for their younger selves from the ninth book.

* CanonForeigner: Edith the lunch lady is an original character for the film. Though she could be a case of DecompositeCharacter with Ms. Anthrope, whose first name is Edith in the books.

* ActuallyPrettyFunny: [[spoiler:Near the end, Mr. Krupp reveals that he dug George and Harold's comics out of the garbage, read them and begrudgingly admits that he thought they were pretty good.]]

* {{Foreshadowing}}: In the opening alone, the boys freeze that moment before Mr. Krupp yells at them to come to his office. His wig is in mid-air, leaving his bald head exposed. In that frame, he resembles Captain Underpants (but angrier and with clothes on).
** Melvin presenting his invention, the Turbo Toilet.

* BrickJoke: To get her attention away from them so they can sneak into the office, George and Harold prank call Ms. Anthrope, telling her she's won a billion dollars, and then put her on hold. As a RunningGag, she's ''still'' waiting for "them" to pick up. [[spoiler:At the very end, '''she's still doing so'''; George and Harold even point out she's been like this for the whole movie, and go back to the phone, which startles her and makes her accidentally hang up, much to her immense anger.]]

* DolphinsDolphinsEverywhere: Harold's love of dolphins becomes a RunningGag.

* PunnyName: Miss Anthrope
* RaceLift: Both Ms. Anthrope and Mr. Fyde are black in this film, compared to in the books where, while they're always monochrome, neither of them have the shade of gray to represent that.
* RapidFireComedy: Just like the books; special mention goes to the SplitPersonality [[https://www.youtube.com/watch?v=3Z1PTR52Km4 scene in the treehouse.]]

* AdaptationDistillation: The film is mainly an amalgamation of the best parts of the first four books in the series, but includes elements from almost all of the books.

* MetaTwist: The primary conflict of the film is Mr. Krupp planning to put the boys in separate classes. So, ''obviously'', the resolution is going to be them reversing it and the two friends sticking together. Not only did the plot line from the books that this conflict seems to be based upon[[note]]Book eleven when Harold fails the final exam and is told he'll have to redo the fourth grade without George[[/note]]end the same way, but that's just what happens in kids' movies. [[spoiler: Except that's not what happens here. Even though they try hard to prevent it, in the end, George and Harold actually ''are'' put into separate classes. And they're alright with that. They realize that their friendship can persist being separated, and even admit that they may have overreacted to the news a bit.]]

* PrankDate: Subverted. [[spoiler:In the end, [[ThrowTheDogABone to do something nice for]] Mr. Krupp, George and Harold send letters to him and Edith the lunch lady, each apparently from the other to coax them to go on a date.]]

* SequelHook: A minor one, [[spoiler:after Professor Poopypants is shrunk, he successfully escapes riding on a bee. Meaning if a sequel is ever made, he'll most likely return. Also, the Talking Toilets make an appearance at the end.]]

* AdaptationalWimp: Melvin, who in the books is a legitimate kid genius who invented a cloning machine, time machine, and fusion machine by himself. He also was smart enough to transfer the Captain Underpants powers into himself and became a superhero defeating the Turbo Toilet 2000 by himself. In the film, his inventions are instead incredibly tacky utilities (like a giant binder to hold all one's other binders), [[spoiler:and his participation in the last act is largely as a pawn of Poopypants rather than genuine malice or hunger for power.]]

* AdaptationalDumbass: Melvin doesn't come close to reaching the ImpossibleGenius he was in the books. For example, in the book's version of the Invention Convention, his project was a printer that could ''print 2D images into living, sentient beings''. Here, his various inventions (along with being things that could more reasonably exist) are all stupid and impractical, like a giant binder designed to hold regular-sized binders. His {{Catchphrase}} in this film is also him cluelessly stating "I don't get it."