History YMMV / KOn

** In Season 2, Episode 13, one of Azuza's dreams features Mio without pupils while watching a horror movie.

** In Season 2, Episode 13, one of Azuza's dreams features Mio gazing at her without pupils as she watches a horror movie.

* NightmareFuel: During the sequence in the first episode of the anime, when Yui is walking down a hall with the "paranormal" clubs, a very dark and sinister-looking girl (looking similar to Enma Ai from ''Anime/HellGirl'') pokes her head out of a door on the left.

* HilariousInHindsight:
** Yui musing ''"Europe? But I thought we're going to London?"'' in The Movie (released in 2011) becomes accurate ever since the successful vote for Brexit in 2016, which severed England's ties to Europe.
** In the original series, particularly in Episode 3 of Season 2, Ritsu wanting to steal the spotlight and become the face of the band. Eight years later, ''K-On Shuffle'' was released featuring the drummer Yukari as the main protagonist!
** Creator/AyanaTaketatsu voices Azusa, who often wears cat ears. Two years after the series aired, Taketatsu voiced Koneko Toujou in LightNovel/HighSchoolDXD, a nekomata who also has cat ears.
** In the bonus episode "Live House!", in the English dub Yui suggests that they get "transforming fighter" costumes. To which someone comments "Like magical girls?". Yui's, Azusa's, and Mio's English voice actresses would later be cast as Sailor Guardians in the Viz redub of ''Anime/SailorMoon''.

* NightmareFuel:
** During the sequence in the first episode of the anime, when Yui is walking down a hall with the "paranormal" clubs, a very dark and sinister-looking girl (looking similar to Enma Ai from ''Anime/HellGirl'') pokes her head out of a door on the left.
** In the second season, they briefly look inside the Occult Club and see a UFO inside. Not really that spooky, but [[FridgeLogic remembering the aforementioned girl]] from the paranormal clubs, one wonders what the deuce is going on in those rooms...
** Being introduced to [[MagicAntidote this show]] [[MoodWhiplash immediately after]] watching ''[[Anime/RebuildOfEvangelion Rebuild Of Evangelion 2.22]]'' or ''[[Anime/DanganRonpa3 Danganronpa 3's Despair Arc]]'' may cause [[TearJerker unexpected]] [[HeroicBSOD problems]] [[Main/KillEmAll when]] ''Tsubasa o Kudasai''" [[SoundtrackDissonance begins to play]].
** In the manga, Sawako scaring Mio during the second training camp ironically leads to Mio [[https://static.tvtropes.org/pmwiki/pub/images/k-on_nightmare_1762.jpg making a]] NightmareFace of her own (though the [[ArtShift particular art style]] is meant to be a ShoutOut to ''Manga/DriftingClassroom''). The anime version [[https://i.imgur.com/IeQiaox.jpg isn't much better]].

* WhatDoYouMeanItsNotForLittleGirls: A very light, comedic slice-of-life doesn't mean the series will have any possible Yuri subtext. There's also Mio's infamous panty shot, which is brought up more than once long after it happened (even though the anime [[AdaptationalModesty makes it less raunchy]]).

** In episode [=1x06=], inside Ritsu's funhouse, there's a statue that looks bizarrely like Bill Cipher, despite ''WesternAnimation/GravityFalls'' still being three years in the future.

* WhatDoYouMeanItsNotForLittleGirls: A very light, comedic slice-of-life doesn't mean the series will have any possible Yuri subtext. There's also Mio's infamous PantyShot, which is brought up more than once long after it happened (even though the anime [[AdaptationalModesty makes it less raunchy]]).

* TheyWastedAPerfectlyGoodPlot: Despite how clear the show is about putting the comedic slice of life elements at the forefront, the most frequent criticism of the anime is that [[ThePiratesWhoDontDoAnything it doesn't focus enough on Houkago Tea Time's musical progress or their music in general]]. Only four songs are introduced in the body of the show, and the band doesn't get popular beyond their own school. This is ultimately is an effect of the original manga, which only introduced these same four songs, of which only "Fuwa Fuwa Time" and "U&I" had lyrics.

** TheMovie's opening. All of the OPs have the characters being cute while playing music etc. but the movie really ramps it up, showing the girls doing almost pointless cute things.

* TheyWastedAPerfectlyGoodPlot: Despite how apparent the show is about putting the comedic slice of life elements at the forefront, the most frequent criticism of the anime is that [[ThePiratesWhoDontDoAnything it doesn't focus enough on Houkago Tea Time's musical progress or their music in general]]. Only four songs are introduced in the body of the show, and the band doesn't get popular beyond their own school. This is ultimately is an effect of the original manga, which only introduced these same four songs, of which only "Fuwa Fuwa Time" and "U&I" had lyrics.

** And then there's Jun, who somehow gets ''even less'' character development than Nodoka, even though she's promoted to a main character in one of the two reboot manga!
* TheyWastedAPerfectlyGoodPlot: A common criticism of the anime is that despite being about a high school band, [[ThePiratesWhoDontDoAnything it doesn't focus enough on the band's musical progress or their music in general]], as opposed to the more common slice of life elements. Only four songs are introduced in the body of the show, and the band doesn't get popular beyond their own school. This is ultimately is an effect of the original manga, which only introduced these same four songs, of which only "Fuwa Fuwa Time" and "U&I" had lyrics.

* TheyWastedAPerfectlyGoodPlot: A common criticism of the anime is that despite being about a high school band, [[ThePiratesWhoDontDoAnything it doesn't focus enough the band's musical progress or their music in general]], as opposed to the more common slice of life elements. Only four songs are introduced in the body of the show, and the band doesn't get popular beyond their own school. This is ultimately is an effect of the original manga, which only introduced these same four songs, of which only "Fuwa Fuwa Time" and "U&I" had lyrics.

* TheyWastedAPerfectlyGoodPlot: A common criticism of the show is that it does not focus enough on progress of the band and their music, as opposed to the more common slice of life elements. Only 4 songs are introduced in the body of the show, and the band doesn't get popular beyond their own school. Which ultimately is an effect of being based off the comic, which only introduced these same 4 songs, of which only Fuwa Fuwa Time and U&I had lyrics in the original comic.

** Fans of {{Mecha}} anime loathe ''K-On!''. They blame it for starting a {{Moe}} boom which saturated the anime industry and also criticize the show's lack of plot and art style. While fans of ''K-On!'' tend to ignore mecha fans, they do contest that ''K-On!'' actually benefitted the anime market and that mecha fans are merely [[NostalgiaFilter blinded by nostalgia]].

** Around the time that both ''Manga/KOn'' and ''LightNovel/HaruhiSuzumiya'' were airing, it was a bad idea to mention both of them in one sentence at websites where fans of those shows were. The odd thing is: While the creators for the manga/light novels are different, they were both made adapted into an anime by the same company, Kyoto Animation. The rivalry stemmed mainly from the fact that both ''K-On!'' and the second season of ''Haruhi'' were produced around the same time, and both (supposedly) suffered for it in terms of quality storytelling. Plus, there were moments in ''Haruhi'' where the characters resembled ''K-On!'''s characters. This rivalry has cooled down over time however, as fans of Kyoto Animation as a whole usually enjoy both for different reasons nowadays.

** Whatever you do, do NOT mention both ''Manga/KOn'' and ''LightNovel/HaruhiSuzumiya'' in one sentence at websites where fans of those shows are. (Since they're mostly infested with trolls.) The odd thing is: While the creators for the manga/light novels are different, they were both made as animes by the same company, Kyoto Animation. The rivalry stems mainly from the fact that both ''K-On!'' and the second season of ''Haruhi'' were produced around the same time, and both (supposedly) suffered for it in terms of quality storytelling. Plus, there are moments in ''Haruhi'' where the characters resembled ''K-On!'''s characters. Ironically, the cover for [[http://www.cdjapan.co.jp/pictures/l/09/47/PCBE-53617.jpg the seventh DVD]] has been critized among ''K-On'' fandom for looking similar to the art style of ''{{Manga/Nichijou}}'', [[Creator/KyotoAnimation KyoAni's]] next project...
** Also, fans of {{Mecha}} absolutely ''loathe'' ''K-On!''. They blame it for spurring on endless {{Otaku}}-pandering [[FollowTheLeader imitators]] in a {{Moe}} boom that saturated the market and has made quality mecha far rarer than it used to be.

** Azusa's guitar solo in [[https://www.youtube.com/watch?v=FGKClJtHHJs Don't Say "Lazy" (5 People Ver.)]] starts very similarly to the main riff of "[[https://www.youtube.com/watch?v=Y1D3a5eDJIs Runnin' Down A Dream]]" by Music/TomPetty.

* AdaptationDisplacement: The manga the anime is based on isn't as popular as the anime. Being a Naoko Yamada directed show by Creator/KyotoAnimation, a lot of [[AdaptationExpansion extra scenes and expanded characterization]] were added to the anime to make it more memorable than its manga counterpart. %%WebVideo/BeatriceTheGoldenWitch does a good job of explaining why the anime overshadows the manga.

** In the manga, Sawako scaring Mio during the second training camp ironically leads to Mio [[https://static.tvtropes.org/pmwiki/pub/images/k-on_nightmare_1762.jpg making a]] NightmareFace of her own (though the [[ArtShift particular art style]] is meant to be a ShoutOut to ''Manga/TheDriftingClassroom''). The anime version [[https://i.imgur.com/IeQiaox.jpg isn't much better]].

** In the manga, Sawako scaring Mio during the second training camp ironically leads to Mio [[https://static.tvtropes.org/pmwiki/pub/images/k-on_nightmare_1762.jpg making a]] NightmareFace of her own. The anime version [[https://i.imgur.com/IeQiaox.jpg isn't much better]].

* NightmareFuel: During the sequence in the first episode of the anime, when Yui is walking down a hall with the "paranormal" clubs, a very dark and sinister-looking girl (looking similar to Enma Ai from ''Anime/HellGirl'') pokes her head out of a door on the left.

** Mugi commits a war crime [[labelnote:Explanation]] A scene where Mugi steals Mio's strawberry off her cake slice, leading to her breaking down in tears. Many fans treated this as if Mugi crossed the MoralEventHorizon [[/labelnote]]

** Being introduced to [[MagicAntidote this show]] [[MoodWhiplash immediately after]] watching ''[[Anime/RebuildOfEvangelion Rebuild Of Evangelion 2.22]]'' may cause [[TearJerker unexpected]] [[HeroicBSOD problems]] when "''Tsubasa o Kudasai''" [[SoundtrackDissonance begins to play]].