* ArchivePanic: The circle has released over 300 [=CDs=] in various series (mostly Music/TouhouFanMusic), so you'll be here for a while. However, its output has slowed down considerably as of TheNewTwenties, so you at least have a chance to catch up.
* SugarWiki/AwesomeMusic: Many of their hits [[AwesomeMusic/TouhouProject are very, very liked]].
* ItsPopularNowItSucks: While they are undoubtedly one of the most popular remix groups, there are those who hate what IOSYS do to the original songs, find their videos annoying, and consider them to be sell-outs for doing things like taking on commercial jobs and selling their [=CDs=] through Amazon.
* MemeticMutation: ''All'' of their ''Touhou'' songs have become parodied on Website/YouTube and Website/NicoNicoDouga in {{Voice Clip Song}}s of things like the Japanese UsefulNotes/McDonalds commercials and Creator/JackBlack's appearance on ''Series/SesameStreet''.
* MisattributedSong:
** Because of their status as the best-known ''Touhou'' remix group, expect the work of other ''Touhou'' remixers such as Silver Forest and Cool&Create to be misattributed to them, especially by the Western fandom.
** On the flip side, because IOSYS does work with arrangers, lyricists, and vocalists from other circles and songs that they've worked on sometimes appear on other circles' [=CDs=], there is occasionally a point of contention as to which circle the song should be considered belonging to (for example, [[https://www.youtube.com/watch?v=X-N6YxVgjok "Mizuhashi Jealoussic Park"]], which originally appeared on [=ALiCE'S EMOTiON=]'s ''Chaos Flare'' album and later on IOSYS's ''Touhou Ageha'').
* ParodyDisplacement: Most people in the West are more familiar with the songs that make fun of the ''Touhou'' universe more than the original songs based on it. Those include the Cirno, Alice and Reisen's theme, respectively.
* SignatureSong:
** "Cirno's Perfect Math Class" and "Marisa Stole The Precious Thing" are two of their most well-known songs.
** Among fans of ''VideoGame/DanceDanceRevolution'', ARM's "ENDYMION" is infamous for being ThatOneBoss.
* TearJerker: "Artificial Children" becomes quite sad when you realize it's about Alice wondering if her dolls have life or not.
%%** The ending of "Alice -> Sweet" certainly qualifies. The MayflyDecemberRomance fanvid really caps it. (Zero-Context Example)
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