Anime First: The series was later adapted into a two volume manga, which was less comedic and even more of a Mind Screw than the original series. An omnibus edition of the manga was released in 2012, featuring an additional story and lots of artwork and character designs.
Channel Hop: The rights to the series was sold by Gainax, by then a troubled company, to Production I.G in 2015. I.G would produce Progressive and Alternative without Gainax' involvement.
While the original series is licensed to Funimation, Progressive and Alternative are owned outright by Warner Home Video.
Colbert Bump: The Pillows received this thanks to the series.
Doing It for the Art: Kazuya Tsurumaki stated that the reason why the series exists was because he and his staff had become burnt out from making End of Evangelion, so they wanted to do something to help them blow off steam.
DVD Commentary: There are Japanese commentaries for all six episodes with the director Kazuya Tsurumaki.
Fan Nickname: After Seasons 2 and 3 were officially titled Progressive and Alternative, fans decided to nickname the original series "FLCL Classic".
Network to the Rescue: Synch-Point went out of business, and for years there were no DVDs after the initial print run of the box set. Luckily, Funimation decided to re-release the series on a single DVD and give it its first ever (American) Blu-ray release. Similarly, after Tokyopop shut down its American division, Dark Horse Comics released an omnibus edition of the manga.
The Pillows were very close in denying working to make music for the series because it felt weird to them to do music for anime outside their comfort zone as a typical music band.
Hideaki Anno revealed in a 2019 interview that he had tried to get Gainax to sign over the rights to the FLCL IP (as well as the GunBuster IP) to him and Studio Khara in exchange for a million-class loan to help the struggling studio away from the edge of bankruptcy. Anno's plans were to let his protégé, Kazuya Tsurumaki, develop new installments for both shows, but much to his outspoken annoyance, Gainax instead straight up duped him and moved the rights to a shell company simply to avoid upholding their end of the bargain.
The English dub for this series may be the only one not set in pre-Meiji times to keep characters' names in Eastern style. This threw off the voice actors a lot, as shown in the outtakes. The manga flips their names to Western style, as does this site.
There was one animation director at Gainax who, for whatever reason, absolutely loved Eri Ninamori. He insisted he be allowed to helm every scene where Ninamori appears. This is why the times she's onscreen look and feel similar to each other, even if the entire rest of an episode is made in a completely different style.
Haruko is left-handed because the director isn't. Tsurumaki believes left-handed people are more interesting and fun.