Adaptation Displacement: The anime adaptation is better known in the Western World than the original manga.
Best Known for the Fanservice: In volume 1's side notes, the author comments that, although chapter 3 introduces Rina and Yuuri, the only thing people seem to want to talk about is Kaito's Shower Scene.
Die for Our Ship: Poor Michal gets hit hard by this from those who ship Kaito and Lucia, with her role in that love triangle being a primary reason for her unpopularity.
Fanon: Lack of character songs for Noel and Coco led to fans adopting other anime songs by their voice actresses (e.g. "Tsubasa" from Kiddy Grade for Noel and "Hana no Sasayaki" for Coco).
The series used to have a huge fanbase in Spain, and it is still remembered at least as well as more successful magical girl series like the mighty Futari wa Pretty Cure. Part of this was due to the sheer effort and high budget that were put on adapting the series, which included character songs performed by an absolute all-star cast of animated music film singers in Spain. Even people who aren't fans of the series (or its songs' music genre) typically acknowledge it had an amazingly well done soundtrack.
Italy also loves the series, and the job they did with its music aspect has almost as many fans abroad as the anime itself.
This show is also very popular in Taiwan, to the point that there's more Mermaid Melody merchandise there than its native Japan nowadays.
Harsher in Hindsight: One thing no one wanted to talk about when the series aired. The entire plot — both the villains' plan and the Lucia/Kaito love story — starts because of a tsunami in the Indian Ocean, which killed Kaito's parents and destroyed the orange mermaid country. A certain real-life tsunami in the Indian Ocean with a similarly high death toll happened the day the anime ended.
Hilarious in Hindsight: The seven mermaid races share their colors with seven of the eight Fairy Tones from Suite Pretty Cure ♪, and given the whole idol shtick... Hell, there's even a love interest to one of the main characters voiced by Daisuke Kishio.
Seira is a beautiful little orange mermaid that certainly steals the fanbases' heart.
In fact, all of the Mermaid princesses, like Lucia Nanami, if not the entirety of "The Mermaid Melody" team. They all have their own way of being adorable.
While significantly good overall, the Spanish dub sometimes has a hard time trying not to fall in Totally Radical. The teenage lingo used for the dialogues was a bit outdated even by the time they distributed the anime in Spain, not to mention when one watches the series today.
The instrumental of Lady Bat's "Ankoku no Tsubasa" strongly echoes "Speed TK Re-Mix", the catchy 1997 J-pop theme used by mixed martial artist Kazushi Sakuraba. Coincidentally or not, Sakuraba is a real life anime fan.
Some European dubs utilize a limited repertoire of songs for several characters. For instance, Lady Bat and the Black Beauty Sisters share songs in some of those versions.
Viewer Gender Confusion: Lady Bat is female but her androgynous looks have caused a lot of confusion, and even arguments, between fans. She was believed by the fans to be a male crossdresser for many years. It was only fairly recently some offical character art confirmed that she's a Bifauxnen woman.
What Do You Mean, It's for Kids?: The more suggestive and bloody manga is rated "13+" in North America, where the Animation Age Ghetto compels manga publishers to put ratings on their books, yet it was originally published in Nakayoshi, a magazine for little girls.
The Italian dub. The voice acting is great, and the songs are possibly better than the Japanese ones. They completely substituted J-pop music for pop-rock and rewritten the lyrics to match the new song. Checkitoutyourselves.
In particular, the song "Assoluto Amore" (lit. "Absolute Love"), the replacement for "Return to the Sea", manages to capture Sara's character perfectly, being an ode to The Power of Lovesung to an angry melody with restrained anger and, near the end, subtly warning it can destroy the world.note the lyrics are "L'Assoluto di un Amore può/cambiare i connotati al mondo". Literally it translates to "The Absolute of a Love can/change the world's face", but "cambiare i connotati" is usually an euphemism for "busting someone's face".
Some countries made Noel's color Indigo, as Aiiro (Deep-Blue), would be hard to translate, and make her too similar to Hanon. Technically, Hanon is aquamarine/turquoise, and not blue, but this often had to be changed too.
confirmed that she's a Bifauxnen woman.