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* AlternateCharacterInterpretation: Although Sam seems like something of a ManicPixieDreamGirl, note that it could be that Charlie's narration sees her at this. So much of the story is about her from his point of view, so it's unknown how much of Sam's real personality we're seeing and how much is Charlie's framed fantasy version of her. Sam herself seems to defy this trope towards the end, where she tells Charlie that ''he'' has to make himself happy instead of putting others before him.
* SugarWiki/AwesomeMusic:
** "It's Time" by Music/ImagineDragons for the trailer.
** Charlie's playlist is pretty awesome too. Full of great 90s songs that set the scene.
** Not to mention "'Heroes'" by Music/DavidBowie as the "tunnel song".
* BestKnownForTheFanservice: Outside the US this movie is known as the movie with Logan Lerman in just briefs grabbing a lingerie clad Emma Watson's breasts onstage.
* HilariousInHindsight: After working with Emma Watson, aka [[Franchise/HarryPotter Hermione Granger]], Ezra Miller entered the Wizarding World in ''Film/FantasticBeastsAndWhereToFindThem''.
* JerkassWoobie:
** Brad is an ArmouredClosetGay who seems to genuinely like Patrick, but has to hide it from his homophobic peers. The fact that his father hit him for kissing Patrick almost makes you forget that he's a JerkJock who publicly calls Patrick a fag.
** Mary Elizabeth is an annoying SoapboxSadie but you do feel a little sorry for her when Charlie (rather dickishly) [[spoiler: kisses Sam right in front of her]].
* LoveToHate: Mary Elizabeth has very few redeeming qualities. But Mae Whitman makes her so hilariously annoying that she's one of the funnest characters in the film.
* MemeticMutation: "I'M BELOW AVERAGE!"
** [[MissingTrailerScene And one from the trailer that didn't make the final cut being]] "Be aggressive! Passive aggressive!"
* NightmareFuel: Charlie's phone call to his sister is one for anyone who's ever had a sibling, friend, or relative with emotional issues.
* OneSceneWonder: Even though Mr Anderson doesn't feature as much in the film as he does in the book, Paul Rudd still makes him memorable. Especially with his story-defining line:
--> "We accept the love we think we deserve."
* OneTruePairing: Although Charlie/Sam is MaybeEverAfter in the book, a lot of fans like to think [[RelationshipUpgrade they got together]]. [[spoiler: Enough for it to be made canon in the film, which was directed [[WordOfGod by the original author]].]]
* RetroactiveRecognition: Ponytail Derek (Charlie's sister's boyfriend) is Cousin Greg from ''Series/{{Succession}}''.
** [[Creator/JuliaGarner Susan]] (Charlie's old friend from middle school) went onto be Ruth in ''Series/{{Ozark}}''
* WhatDoYouMeanItsNotForKids: Just because "family-friendly" actress Creator/EmmaWatson appears here, it doesn't mean the film wasn't (briefly) rated R for "teen drug and alcohol use, and some sexual references" (it would be re-certified with a PG-13 certificate a few months before its release).
* UnintentionallySympathetic: Perhaps more of an InformedFlaw, but in the extended book version of Sam's ReasonYouSuckSpeech to Charlie, she tells him he was a bad friend for simply going along with Patrick's self-destructive nights of cruising and drinking while mourning his breakup with Brad. While Sam is correct that Charlie didn't do anything to stop Patrick and that he inadvertently enabled him, she is also ignoring that Charlie is younger and more naive than Patrick – a fact they've known since they met him, since they made a point of showing him the high school ropes – and she's somehow expecting him to know better than Patrick and be able to pull him out of a depressive spiral. Charlie's inaction isn't a shining moment, but he also didn't force Patrick to do the things he was doing. Considering her friend group introduced Charlie to drinking and recreational drug use, expecting him to then recognize and stop Patrick's self-destruction – when none of his older or more experienced friends did either – is unfair.
* UnintentionallyUnsympathetic: Sam, again with regards to her ReasonYouSuckSpeech to Charlie. In both the book and the movie, the fact that it turns into a ReasonYouSuckSpeech feels like it goes way too far. Yes, Charlie should be called out on being too passive. But the fact that it starts because Sam is offended because he didn't ask her out immediately after Craig broke her heart is a silly reason. It's not exactly strange to wait a while until your friend is over being cheated on and humiliated to want to ask them out, and Sam sort of tears into Charlie for listening to her exact advice (asking lots of questions and letting others do the talking) ''too well,'' which comes across like Sam wanted Charlie to be able to read people's minds.
* TheWoobie:
** Charlie begins the story having just lost his best friend to suicide, and he already has several social anxiety issues. When the group turns on him briefly over his break-up with Mary Elizabeth, you just want to give the poor guy a hug. To say nothing of [[spoiler: discovering he was molested as a child by the aunt he looked up to. And ''he'' feels guilty for ''her'' death]].
** Sam is revealed to [[spoiler: have also been molested by one of her father's colleagues. And of course she did love Craig but he was cheating on her the whole time]].
** Patrick appears to be ThePollyanna but becomes an even bigger Woobie as the story goes on. He's comfortable with being gay but he had to watch the boy he loves attacked just for loving him back - and said boy then denies that they were ever an item to save face in front of his friends.
** Candace as well to a lesser extent, as her major subplot is cut out of the film. But she is shown getting hit by her boyfriend. [[spoiler: She ends up pregnant and has to abort it]]. That's not to mention her look of horror when Charlie calls her near the end of the film.
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