* AdaptationDisplacement: The anime adaptation is better known in the Western World than the original manga.
* BestKnownForTheFanservice: 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 ShowerScene.
* DieForOurShip: 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 [[TheScrappy unpopularity]].
%%* EnsembleDarkhorse: Rina, Sara and the Black Beauty Sisters.
* {{Fanon}}: Lack of character songs for Noel and Coco led to fans adopting other anime songs by their voice actresses (e.g. "Tsubasa" from ''Anime/KiddyGrade'' for Noel and "Hana no Sasayaki" for Coco).
* FauxSymbolism: The religious imagery in Lucia's name.
* GermansLoveDavidHasselhoff:
** 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 ''Anime/FutariWaPrettyCure''. 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.
* HarsherInHindsight: 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.
* HilariousInHindsight: The seven mermaid races share their colors with seven of the eight Fairy Tones from ''Anime/SuitePrettyCure'', and given the whole idol shtick... Hell, there's even a love interest to one of the main characters voiced by Creator/DaisukeKishio.
* {{Moe}}:
** 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.
* {{Narm}}:
%%** The Baby/Coral Fairy from episode 36.
** While significantly good overall, the Spanish dub sometimes has a hard time trying not to fall in TotallyRadical. 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.
* NightmareFuel: Near the end, [[spoiler:[[NotSoHarmlessVillain Fuku-chan]] reveals the truth with a horrifying NightmareFace and a menacing [[BattleAura purple dark aura]] and subjects his "master" to DemonicPossession without a fuss.]] BewareTheSillyOnes indeed.
* {{Padding}}: Like with many Magical Girls shows, the transformation sequences are lengthy and often recycled.
* PeripheryDemographic: Teenage girls, especially in the Western audience.
* {{The Scrappy}}: Michal is extremely despised by fans for [[DieForOurShip getting in the way of the pairing of Luchia and Kaito]], her obsessive clinginess towards the later, and being [[UngratefulBitch ungrateful]] for everything her brother Rihito did to make her life better.
* {{Squick}}: Some see the fanservice as this, considering the series is still technically aimed to little girls, and most of the characters are around 13.
* StrangledByTheRedString: Caren with Subaru, an anime-only character probably introduced only so people would stop slashing her with her sister.
* SuspiciouslySimilarSong:
** 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 Wrestling/KazushiSakuraba. 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.
%%* ThatOneBoss: "Aurora no Kaze ni Notte" in the video game ''Pichi Pichitto Live Start''.
* ViewerGenderConfusion: 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 [[https://mermaidmelody.fandom.com/wiki/Lady_Bat#cite_note-1 some offical character art]] confirmed that she's a {{Bifauxnen}} woman.
* WhatDoYouMeanItsForKids: The more suggestive and bloody manga is rated "13+" in North America, where the AnimationAgeGhetto compels manga publishers to put ratings on their books, yet it was originally published in ''Nakayoshi'', a magazine for little girls.
* {{Woolseyism}}:
** 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. [[https://www.youtube.com/watch?v=ABYYYaI9A-4 Check]] [[https://www.youtube.com/watch?v=I_7gjazsNEU&feature=related it]] [[https://www.youtube.com/watch?v=zpUnhODes24&feature=related out]] [[https://www.youtube.com/watch?v=hC9hRl1E9UQ&feature=related yourselves]].
*** 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 ThePowerOfLove [[LyricalDissonance sung 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".[[/note]]
** 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.
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