* ActingForTwo:
** Ile and Nell are both voiced by Chinatsu Akasaki in Japanese and by Lara Woodhull in English.
** In the Japanese version, in addition to voicing Isabella in the anime's first season, Harumi Sakurai voices Katerea Leviathan in the ''New''.
** Akeno Himejima and her mother Shuri are both voiced by Creator/ShizukaIto in Japanese.
** In the English dub of ''[=BorN=]'', Grayfia and Ophis are both played by Megan Shipman.
* BannedInChina: The anime adaptation of ''DXD'' was refused classification in New Zealand, on the count that it "promotes child pornography". On the other hand, the series is available in Australia. The anime has been banned in China as well for excessive sexual content and graphic violence.
* CastingGag:
** It's not the first time Creator/AyanaTaketatsu (Koneko's [=VA=]) has voiced a cat [[Manga/CatGod before]].
** The same goes for Koneko's English actress Creator/JadSaxton, as she previously voiced a cat, [[Manga/FairyTail except she came from a different universe]].
* ChannelHop: An animation studio variation. {{Creator/TNK}} handled the animation production for the first three seasons, with Tetsuya Yanagisawa as director. For ''Hero'', the series was produced by Passione with a completely new crew and was directed by Yoshifumi Sueda.
* CreativeDifferences: Disagreements between Tetsuya Yanagisawa and Ichiei Ishibumi over adapting volumes 5 through 7 for ''[=BorN=]'' led to them going their separate ways after the season was broadcast. Ishibumi also wrote ''EX'' so that the last four episodes of the season became an AlternateContinuity.
* CreatorBacklash: After ''[=BorN=]'' was broadcast, Tetsuya Yanagisawa and Ichiei Ishibumi both admitted it wasn't the season they were hoping for because the former changed elements of the light novel's fifth through seventh volumes for the season, which didn't go over very well with Ishibumi and Takao Yoshioka. Then, Ishibumi wrote the ''EX'' spin-off to turn it into an AlternateContinuity before he and Yanagisawa went their separate ways. ''[=BorN=]'' would turn out to be the last season with which Yanagisawa and TNK were associated.
* CrossdressingVoices: Creator/AyaneSakura voices Gasper Vladi, though [[DudeLooksLikeALady one would be forgiven to think otherwise]].
* DeletedScene: There are extra scenes in ''New'' that didn't make the broadcast run due to time limitations, but were restored for the Blu-ray/DVD releases.
* DirectedByCastMember: Three cast members directed the English dub of the anime. The first was by Creator/ColleenClinkenbeard, who voiced Shiro and Xuelan; the second by Creator/ChristopherSabat, who voiced Ddraig; and the third by Cris George, Creuserey Asmodeus's English VA.
* DoingItForTheArt: During the production of ''Hero'', Ishibumi had the Passione staff read nearly all of the light novels so that they don't miss any inaccuracies.
* ExecutiveMeddling: At one point during volume 3, Ishibumi intended to have Issei suck Rias's breasts, but Fujimi Shobo unsurprisingly nixed that idea.
* FlashbackWithTheOtherDarrin: For the dub of ''[=BorN=]'', all of Scott Freeman's dialogue as Issei in the flashbacks were redubbed by Josh Grelle due to erratic behavior on Freeman's part.
* FanNickname:
** Hypnobutt - Koneko [[MaleGaze swaying her butt on the screen in the ending]]
** Weapon [[{{Netorare}} NTR]] - [[spoiler: for Issei and Kiba ''hijacking'' both True Longinus and ''all'' of Siegfried's swords respectively.]]
** GAR-sper - In some circles, Gasper after his awesome moment in Volume 10.
** [[Manga/{{Bleach}} Kenpachi dragon]] - Grendel is called this in the {{Imageboard}}s thanks to his BloodKnight attitude while fighting Issei.
** Dragon swag - What fans refer to when Issei attracts someone's attention.
** Dickora - for Diodora, which further cements his HateSink status.
* IKnewIt:
** Some people got it correct when [[spoiler:they thought that Great Red was going to help out both Issei and Ophis. ''No one'', however, thought that Great Red has a {{Delinquent}} personality.]]
** Quite a few people guessed correctly that Passione [[http://www.animenewsnetwork.com/news/2017-10-21/high-school-dxd-hero-anime-promo-video-streamed/.123018 will animate the fourth season]].
** Many fans have already guessed that Issei would have children with his harem. They were right.
** When the first episode of ''Hero'' was premiered in March 2018, a few Japanese viewers correctly guessed that the series would eventually retcon ''[=BorN=]'' out of existence with Life 0's adaptation of Volume 6.
* ImageSource:
** BewareTheNiceOnes/AnimeAndManga (manga)
** HaremSeeker (manga)
* {{Jossed}}: Although ''EX'' involved Loki creating the AlternateContinuity the last four episodes of ''[=BorN=]'' take place in, it doesn't involve Issei's children undoing ''that'' particular timeline.
* RealLife/MeanCharacterNiceActor:
** Creator/HitomiNabatame and Felecia Angelle voice Raynare, but they are known to be charming and affable in real-life.
** In contrast to playing Riser Phenex, Creator/TakehitoKoyasu and Creator/ChristopherCoreySmith are shown to be friendly persons.
** And Shalba Beelzebub was voiced by Creator/KenNarita and Creator/IanSinclair, who are also known to be very generous as interviews can attest.
* NamesTheSame: Sister Asia Argento shares the same name with the famous Italian actress Creator/AsiaArgento.
* NetworkToTheRescue: The backlash against ''[=BorN=]'' led to Passione animating the fourth season, ''Hero'', and included the same voice cast, sound director and composer to boot.
* NoExportForYou:
** The licensed games for the 3DS and PS Vita have only been exclusive to Japan.
** The anime wasn't released in China or New Zealand anytime soon due to its violence and sexual content.
* OldShame: Tetsuya Yanagisawa and Ichiei Ishibumi came to see ''[=BorN=]'' as a noose around their necks.
* TheOtherDarrin:
** For the dub of the final Tetsuya Yanagisawa/Takao Yoshioka/Junji Goto/TNK season:
*** Due to Scott Freeman's arrest for child pornography in late 2014, Creator/JoshGrelle voices Issei, cementing him as the ''de facto'' voice actor for the character.
*** Kelly Angel replaced Teri Rogers as Akeno. The dub acknowledges this in a very ''Series/{{Roseanne}}'' like way in the second episode.
--> '''Venelana''': You sound so different, Akeno!
*** Megan Shipman replaced Krishna Smitha as Grayfia due to Smitha being involved in mostly union-only projects after moving to Los Angeles.
** For ''Hero'', Mikako Takahashi provides the voice of Venelana instead of Mari Shiraishi.
* PlayingAgainstType:
** In the dub, the cultured and flirty Devil Rias Gremory is voiced by the [[{{Lust}} lustful]] and [[SirSwearsALot foul-mouthed]] FallenAngel [[Anime/PantyAndStockingWithGarterbelt Panty Anarchy]].
** Again with the dub, the perverted nice guy Issei Hyoudou is voiced by [[WebComic/AxisPowersHetalia United Kingdom]], the [[MeanBrit fake]] [[QuintessentialBritishGentleman British gentleman]]. At least, [[RoleEndingMisdemeanor for the first]] [[TheOtherDarrin two seasons]].
*** For the third season, Issei gets ''two'' Playing Against Types: [[Creator/JoshGrelle he is voiced by]] the fearful UnluckyEverydude [[Manga/FutureDiary Yukiteru Amano]], as well as [[LightNovel/InfiniteStratos Ichika Orimura]], the one guy in an all-girls academy who has an UnwantedHarem [[CluelessChickMagnet and is all the oblivious about it]].
* RelationshipVoiceActor:
** Although it was a short-lived one, Creator/ShizukaIto and Creator/HitomiNabatame reunite here as Akeno and Raynare.
** Creator/ScottFreeman and Creator/JamieMarchi played another OfficialCouple in ''LightNovel/BakaAndTestSummonTheBeasts'' (Yuuji and Shouko).
** ''New'' reunites [[Creator/AyaneSakura Akane Isshiki]], [[Creator/MaayaUchida Rei Kuroki]] and [[Creator/HarukaYamazaki Mizuha Amagi]] from [[Anime/VividredOperation Vividred Operation]] but ironically their characters will never get to interact with each other in the anime.
** Also in ''New'', [[Creator/YokoHikasa Emilia Justine]] [[LightNovel/TheDevilIsAPartTimer and]] [[Creator/RyotaOhsaka Satan Jacob]] are reunited but at least this time, Emilia isn't out for Sadao's blood. But if Issei is hurt...
*** [[Creator/AzumiAsakura Emerlda]] was already there. [[Creator/HirokiYasumoto Albert]] pops up to but he's evil now.
*** Remember that [[BadassBystander awesome convenience store worker]] that threw paint balls at Emilia's attacker? He's [[Creator/YuuichiIguchi Saji]] over here.
** [[Creator/HirokiYasumoto Kokabiel]]: [[Creator/YuukiKaji Issei]], [[LukeIAmYourFather I am your father.]] [[Anime/AquarionEvol 12,000 years ago...]] And he's also [[VideoGame/AsurasWrath Asura]]. Though he got demoted from demi-god to fallen angel, no ''wonder'' the Gremory team couldn't even scratch him.
** [[Creator/YuukiKaji Issei]] and [[Creator/YuuichiNakamura Sairaorg]] have ''a lot'' in their list. [[Manga/LaughingUnderTheClouds Fortunately,]] [[VideoGame/FinalFantasyXIII they're]] [[Anime/GuiltyCrown allies]] [[Anime/AquarionEVOL this]] [[Anime/{{Durarara}} time]] [[Anime/FairyTail instead]] [[Anime/NobunagaTheFool of]] [[Anime/NobunagaConcerto enemies.]]
** Quite a lot of the voice actors present were also involved in VideoGame/StreetFighterV - [[Creator/YokoHikasa Rias]] was Laura, Taketora (Dohnaseek) was Akuma, [[Creator/JunichiSuwabe Lucifer]] was Vega, [[Creator/KentaMiyake Mil-tan]] was Zangief, [[Creator/HirokiYasumoto Kokabiel]] was Guile, Ryota Takeuchi (Albion) was Abigail, [[Creator/KosukeToriumi Cao Cao]] was Nash, [[Creator/FumihikoTachiki Ddraig]] is Gill.
** [[Creator/YuukiKaji Issei]], [[Creator/AyaneSakura Gasper]], [[Creator/JunichiSuwabe Lucifer]] and [[Creator/KentaMiyake Mil-tan]] are [[Manga/MyHeroAcademia Todoroki , Ochako, Eraser Head and All Might]].
** For the dub, [[Anime/PantyAndStockingWithGarterbelt the Anarchy Sisters]] reunite in the third season as [[Creator/JamieMarchi daughter (Rias/Panty)]] and [[Creator/MonicaRial mother (Venelana/Stocking)]].
* RoleEndingMisdemeanor: Creator/ScottFreeman originally voiced Issei Hyoudou in the dub of the first two seasons. When he was arrested and convicted for possession of child pornography in 2015, Creator/JoshGrelle replaced him for the third season.
* ScrewedByTheNetwork: When Tetsuya Yanagisawa changed the plots of volumes 5 to 7 substantially for the third season of the anime. It contributed to Ishibumi and Yanagisawa mutually going their separate ways.
* SleeperHit: Of the {{Winter 2012 Anime}} season. No one expected that the series would even sell 10,000 DVD [=/=] Blu-ray copies in the first week! [[AndYouThoughtItWouldFail Hoo, boy, were they wrong]].
* WhatCouldHaveBeen:
** Supposedly, one of Issei's power-ups was to ''suck Rias' breasts''. Unfortunately, that was enough for Fujimi Shobo to say that it was too much for them, so Ishibumi resorted to something else.
** Ishibumi has said that he almost wanted to make Kiba as the main character instead of Issei. However, that didn't come into fruition.
** Ishibumi considered resurrecting Freed with the Holy Grail, and bonding his soul to an evil dragon. He ended up deciding to let him stay dead.
** ''[=BorN=]'' was originally going to last longer, given the extent of the light novel volumes it would cover (volumes 5 through 7). However, this season played the TwelveEpisodeAnime trope straight when Tetsuya Yanagisawa changed the plot elements ''substantially'' to fit the episode timeframe. That decision led to Yanagisawa and Ishibumi going their separate ways and Passione replacing TNK as the main animation studio.
* TheWikiRule: [[http://highschooldxd.wikia.com/wiki/Main_Page Sure thing, dawg!]] '''WARNING:''' Gets a little NSFW in some places.
* WordOfGod: Series creator Ichiei Ishibumi, who contributes to his Twitter feed and light novel afterwords to explain some important aspects of the series like character histories and has answers to questions regarding character names.
* WrittenByCastMember: Creator/JamieMarchi, Rias's English voice actor, wrote most of the scripts for the dub.