* {{Expy}}: Issei's design is actually based on [[Anime/SCRYed Kazuma]] because the author is a fan of the series.
* 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.
* 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.]]
* NamesTheSame: Sister Creator/AsiaArgento
* NamesToKnowInAnime:
** YuukiKaji is Issei Hyodo, [[{{Irony}} ironically]] [[PlayingAgainstType making him an anti]] [[GuiltyCrown Shuu]]. Oh, and [[Manga/AttackOnTitan he fights titans in another dimension.]]
** Creator/YokoHikasa is Rias Gremory [[{{Irony}} ironically]] the one [[KoreWaZombieDesuKa reviving the Dying protagonist]].
** Creator/ShizukaIto is Akeno Himejima, ironically becoming a half-devil after [[Manga/DGrayMan undertaking a career as exorcist.]]
** Creator/KenjiNojima is Yuto Kiba, [[{{Irony}} ironically]] being the calm person compared to say, [[TheLastRemnant Rush Sykes]].
** Creator/AyanaTaketatsu is Koneko Toujou (and [[KOn she keeps the cat motif]], too!)
** AzumiAsakura is Asia Argento, [[{{Irony}} ironically]] [[VideoGame/TheIdolmaster not shy around guys.]]
** Creator/HitomiNabatame is Raynare
** Creator/TakehitoKoyasu is Riser Phenex
** Creator/FumihikoTachiki is Red Dragon Emperor Ddraig, making him the real [[Manga/{{Bleach}} Kenpachi]] dragon.
** Creator/JunichiSuwabe is Sirzechs Lucifer. [[VisualNovel/FateStayNight GARcher]] became a Demon Lord.
** Creator/RikiyaKoyama is Azazel. Why Issei is [[CrazyAwesome crazily awesome?]] He's got [[Manga/MahouSenseiNegima Jack Rakan]] as his mentor.
** [[Creator/MaayaUchida Maaya Uchida]] is Irina Shidou. This makes her a [[RunningGag Self Proclaimed Angel]] with an [[LightNovel/ChuunibyouDemoKoiGaShitai 8th grader syndrome.]]
** [[Creator/RyotaOhsaka Ryota Ohsaka]] is Vali. Guess [[LightNovel/TheDevilIsAPartTimer Sadao]] had a dragon in him all the time.
** Creator/HirokiYasumoto is Kokabiel. See RelationshipVoiceActor below.
** Creator/ShowHayami is the Patriach of the Gremory family.
* RelationshipVoiceActor:
** Although it was a short-lived one, Creator/ShizukaIto and Creator/HitomiNabatame reunite here as Akeno and Raynare.
** Creator/ScottFreeman and JamieMarchi played another OfficialCouple in ''LightNovel/BakaAndTestSummonTheBeasts'' (Yuuji and Shouko).
** The 2nd season of the anime reunites [[AyaneSakura Akane Isshiki]], [[Creator/MaayaUchida Rei Kuroki]] and [[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 the 2nd season of the anime, [[Creator/YokoHikasa Emilia]] [[LightNovel/TheDevilIsAPartTimer and]] [[Creator/RyotaOhsaka Sadao]] are reunited but at least this time, Emilia isn't out for Sadao's blood. But if Issei is hurt...
*** [[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 [[YuuichiIguchi Saji]] over here.
** [[Creator/HirokiYasumoto Kokabiel]]: [[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.
* PlayingAgainstType:
** In the dub, the cultured and flirty Devil Rias Gremory is voiced by the [[{{Lust}} slutty]] and [[SirSwearsALot foul mouthed]] FallenAngel [[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]].
* SleeperHit: Of the {{Winter 2012 Anime}} season. Heck, no one expected that the series would even sell 10,000 DVD [=/=] Blu-ray copies in the first week!
* WhatCouldHaveBeen: Supposedly, one of Issei's power-ups was to ''suck Rias' breasts''. Unfortunately, that was already too much for Fujimi Shobo, so the author resorted to something else.
* TheWikiRule: [[http://highschooldxd.wikia.com/wiki/Main_Page Sure thing, dawg!]] '''WARNING:''' Gets a little NSFW in some places.