* AscendedFanon: The producers of this film openly admitted that they turned Cloud from the serious hero into the brooding loner because the fans would be familiar with this image of him.
* CelebrityVoiceActor:
** Japanese:
*** Ayumi Ito as Tifa Lockheart
*** Masachika Ichimura as Red XIII
** English:
*** Steve Burton as Cloud Strife
*** Creator/RachaelLeighCook as Tifa Lockheart
*** Creator/ChristyCarlsonRomano as Yuffie Kisaragi
*** Creator/MenaSuvari as Aerith Gainsborough, replacing actress and singer Music/MandyMoore from ''VideoGame/KingdomHeartsI''
*** Creator/GeorgeNewbern as Sephiroth, replacing Creator/LanceBass of popular boyband Music/{{NSYNC}} from ''VideoGame/KingdomHeartsI''
*** Rick Gomez as Zack Fair
*** Although a case of RetroactiveRecognition, Creator/ArielWinter as Marlene Wallace.
* ChildrenVoicingChildren: Marlene, Denzel, and the rest of the child characters are voiced by child actors in most languages.
* ColbertBump: Sephiroth's inclusion in ''VideoGame/SuperSmashBrosUltimate'' caused a resurgence of interest in the movie, mainly because his trailer has many sequences recreating moments from ''Advent Children'', while even using its version of "One Winged Angel".
* DuelingWorks: With ''VideoGame/TheLegendOfZeldaTwilightPrincess'', as a continuation of the rivalry between their predecessors, with both works taking on a more "realistic" aesthetic and giving their respective protagonists (Cloud and Link) a [[AnimalMotifs wolf]] motif. Both works were successful commercially, but ''Twilight Princess'' was met with universal acclaim and continued to be quite well-regarded over the years (if not to SacredCow levels like ''VideoGame/TheLegendOfZeldaOcarinaOfTime''), whereas ''Advent Children'' was very divisive (granted, [[VideoGameMoviesSuck its format]] didn't do it very many favors).
* LimitedSpecialCollectorsUltimateEdition: The original CE of the movie was available only in a limited run in Japan, and equated to around $300. It included the ''Last Order'' OVA, a cap and t-shirt with the Fenrir symbol printed on each, a Play Arts ''FFVIIAC'' Cloud with Fenrir, the voiceover script, a special reprint of the [[VideoGame/FinalFantasyVII original game]] and the movie itself, complete with director's commentary and a special features disc. An American equivalent would be released much later, with many of the physical extras (save for the OVA) removed. ''FFVIIAC Complete'' also somewhat qualifies, considering the approximately 20 minutes of new footage and the ''On The Way To a Smile'' OVA.
* MissingTrailerScene: The first 2 trailers are infamous for being made almost entirely of test footage, none of which was used in the final movie (save the scene relating to Aerith's death). Interestingly, some screenshots of these scenes are actually on the back of the original DVD box.
* NoDubForYou: An interesting subversion happens in Latin America: Originally, the film only was released as a home video release in that region, and without a dub, as result of both a lack of the mentioned theater release and the fact that neither Square Enix nor the local distributors managed to get a TV deal with any Latin American broadcasters, which likely had forced them to include a dub, through there were plans to do a Mexican-made dub done in Cuernavaca, which never materialized. However, as a result of the newer 2024 worldwide re-release of the film, not only the movie will get a Latin American theater release, but also a local Spanish dub as well.
* NoExportForYou: ''Complete's'' vocal theme, "Safe and Sound," is not in Western releases of the film, which is odd considering that the song is written by Gerard Way from Music/MyChemicalRomance and sung entirely in English. Furthermore, it's only available on the Japanese iTunes. "Calling" from the original version was used for the Western release.
* TheOtherDarrin:
** For the English release:
*** Creator/GeorgeNewbern took over for Creator/LanceBass[[note]]Yes, of Music/{{NSYNC}} fame[[/note]] as Sephiroth starting with this movie.
*** For ''Complete'', Aaron Refvem and Creator/ArielWinter replaced Benjamin Bryan and Grace Rolek's Denzel and Marlene since the latter two actors aged out of their roles.
*** Music/MandyMoore had also voiced Aerith in the first ''Franchise/KingdomHearts'' game but was replaced by Creator/MenaSuvari for this one.
** For the Japanese release of ''Complete'', Kazumu Izawa and Creator/SumireMorohoshi replace Kyousuke Ikeda and Miyū Tsuzurahara as Denzel and Marlene.
* RecursiveAdaptation: ''Advent Children'' is TheAnimeOfTheGame ''VideoGame/FinalFantasyVII'', being a SequelInAnotherMedium. And then the movie will be adapted in video game form as part of the upcoming [[VideoGameRemake mobile game remake]] ''VideoGame/FinalFantasyVIIEverCrisis''
* ReferencedBy: ''VideoGame/Persona5 Royal'' includes a card game called "Tycoon". If Futaba is one of the players, she may occasionally say "Shall I give you this pair?" when she plays a pair of cards.
* TechnologyMarchesOn: ''Advent Children'' may be a futuristic movie, but the characters use flip cellphones! This movie was released in 2005. The first smartphone would not come out until 2007. At the time, the flip cellphones used in the movie seemed advanced and futuristic.
* ThrowItIn: Several minor aspects of the film, such as Rude's extra sunglasses, were tossed out by development staff as random ideas not in the original concepts, and got approval.
* WhatCouldHaveBeen:
** The initial choice for Denzel's Japanese voice actor was Creator/KoukiUchiyama. However, he was a bit too old to fit the bill, but Creator/TetsuyaNomura later used him in ''VideoGame/KingdomHeartsII'' as the voice of Roxas and later in ''VideoGame/KingdomHeartsBirthBySleep'' as Ventus.
** At a very early stage in development, the only featured characters were going to be Cloud, Tifa, Kadaj, and Sephiroth. The run-time was also planned to be far lower than in the final movie; early interviews mentioned around the 40-minute mark. This would change as it became apparent that fans were expecting ''much'' more than the initial script apparently had, prompting a fairly extensive rewrite. The TGS 2003 trailer, and the unused footage it contains, probably comprises the remains of that early version of the movie.
** WordOfGod says Cloud's new LimitBreak was named "Omnislash Version 5" because it was the fifth version they had come up with. One wonders what the unseen others looked like...
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