* AdaptationDisplacement: Few people know that ''Flowers'' was originally a short story.
* FreudWasRight: Poor Charlie. Upon seeing his sister in the bathtub as a child, was struck by her (seeming) lack of genitalia. Not only did he come to the conclusion that their parents [[{{GroinAttack}} removed it to punish her]], but his mother caught him and...[[BrotherSisterIncest jumped to the wrong conclusion.]] This earned him a traumatic experience with a knife and a deep-seated fear that he'd be castrated one day as well. Anytime he tries to have sex, bam! Traumatic memories.
* HoYay: The cuddling Warren inhabitant boys.
* ItWasHisSled / AllThereIsToKnowAboutTheCryingGame: One of the few things people who haven't read the book know about it is that Charlie is a retarded man who becomes intelligent [[spoiler:and reverted back to how he was beforehand.]] The fact that [[FlowersForAlgernonSyndrome there's a trope]] on ThisVeryWiki named after the story [[NiceJobBreakingItHero probably isn't helping.]]
* NightmareFuel: In the 1968 movie adaptation, Charlie's mental breakdown which involves him running from his older self. The music and the creepy smile of the other Charlie are unsettling enough, but then Charlie gets trapped in a maze and at one point, he's struggling to escape down a long hallway while the other Charlie slowly approaches him. That whole scene is genuinely terrifying.
* ShootTheShaggyDog
* SomeAnvilsNeedToBeDropped: The book is very clear that the treatment of the mentally disabled by abled people is horrific. Things actually have improved in the treatment of the developmentally disabled since then - and probably at least partially as a result - In the 1950's it was very common for families to send away these folks. Nowadays its more acceptable to have a special needs child.
* TheWoobie: Charlie, obviously. [[spoiler:Realizes that his so-called friends were simply using him as a toy, finally reaches genius levels of intelligence, only to lose it, and starts to forget almost all the notable events that happened to him towards the end.]]