* As Ryuko is [[spoiler:falling back to Earth]] in the final episode of ''Anime/KillLaKill'', Satsuki runs towards her. There was originally no dialogue, but Satsuki's voice actor felt this was out of place, so she screamed "[[SayMyName RYUKO!]]" as Satsuki ran. The directors felt it added something to the scene, and left it in.
* It's not dialogue, but when ''Anime/DigimonTamers'' head writer ChiakiKonaka saw that Jianliang's little sister, Xiaochun, was included in the opening song's shot of characters holding up their Digivices, he decided to make her a Tamer. Similarly, when he saw that the character designer had drawn so many pictures of her infamous "[[CutenessProximity Terriermon torture]]", he decided "it would be criminal" not to include scenes of it. Xiaochun and Terriermon even have an ImageSong together.
* In-universe example in ''Manga/MidoriDays'': Seiji and his gang of delinquents get hired to play minor parts in a movie starring their favorite actor. During the final scene, the hero is mortally wounded. The boys are supposed to have a big mourning scene as he dies, but [[LostInCharacter get a little]] ''[[LostInCharacter too]]'' [[LostInCharacter into the moment]], and beat the crap out of the guys who "shot" him in revenge first. The director decides to keep it.
* Because most anime is animated first and then dubbed to fit with ADR, in contrast to the Western practice of recording the voice first and then animating to the voice, there is a tendency for dialogue to be more ad-libbed.
** When Creator/NorioWakamoto was brought in to record the voice of Chiyo-chan's "father" in ''Manga/AzumangaDaioh'', all of his scenes had already been scripted and animated. While he kept to the scripted lines, his delivery invariably ran longer than the animation (in one case, ''over a full minute'' longer). Rather than rerecord his lines, they reanimated the scenes to match them, because he's [[PhysicalGod Norio Effin' Wakamoto]].
* When Jan Valentine in the ''{{Hellsing}}'' OVA storms into the Council of Twelve's meeting room and faces a dozen weapons pointed in his direction, the original voice actor doesn't say anything before being shot. The English dub VA however ad-libs in a hilarious 'Oh f*ck me' comment.
* ''Anime/LupinIII'': The Funimation dubs of the ''Lupin III'' films and specials feature a lot of this.
** ''Anime/LupinIIICrisisInTokyo'' isn't a particularly funny movie in the native Japanese, but the dub had a ton of ad-libbing done by the actors (though not to the point of it being a GagDub), particularly Creator/ChristopherSabat, who voiced Jigen. It worked; it's one of the funniest Lupin movies ever released in the states.
* In ''Manga/LuckyStar'', Tsukasa's voice actress Creator/KaoriFukuhara said the directors encouraged ad-libs. Her famous "barusamiko-su"[[note]]"Balsamic vinegar" -- Tsukasa's VerbalTic in the anime[[/note]] line was one of those moments.
* According to legend, the names of the main characters (A-Ko, B-Ko, and C-Ko) in ''ProjectAKo'' began because the creators couldn't think up good names for the characters, and started referring to them as A, B, and C during preproduction.
* In ''{{Durarara}}'', the kitty ears on Celty's helmet was originally a joke by Narita, but it was kept because the character designer really liked it.
* The ''Manga/AxisPowersHetalia'' anime apparently has a lot of this too. France and England's seiyuus Creator/MasayaOnosaka and Creator/NoriakiSugiyama said in an interview that most of their characters's fights are ad-libbed.
** Which is how we get gems like:
-->'''England''': GET BACK HERE, YOU [[CheeseEatingSurrenderMonkeys CHEESE EATING SURRENDER MONKEY]]!
-->Or:
-->'''England''': My country has produced quality film material...
-->'''France''': I'm sorry, but [[Series/DoctorWho time-travelling police boxes]] can only go so far!
* In ''Anime/AfroSamurai'', following the death of [[spoiler: Brother 1]], Ninja Ninja's "eulogy" ("Add one mo' body to the body toll, may God rest this po' bastard's soul") was impromptu on Creator/SamuelLJackson's part.
* The Japanese version of ''SonicX'' used this a few times. There is a scene in "Super Sonic Appears" where it looks like Sonic is going to get killed. His robot servants ask him if Sonic will survive to which Eggman was meant to have stayed silent (in thought of whether he could actually kill Sonic or not) however the voice actor jokingly said (in Japanese of course): "Of course! No one ever dies in animes!" The other voice actors decided to just go along with the joke causing the scene below to accidentally get created; the show's makers found the scene so humorous that they ended up keeping it in.
--> '''Robot 1:''' "Sir... will Sonic survive?"
--> '''Eggman:''' "Of course! No one ever dies in animes!"
--> '''Robot 2:''' "Animes?"
--> '''Eggman:''' "Of course! [[FailureIsTheOnlyOption The good guy never gets killed in an anime and the bad guy like myself never wins. In other words, not matter how hard we try, the show makers will always make us lose!"]]
* ''LightNovel/HaruhiSuzumiya'':
** During the "Day of Sagittarius" episode, each of the SOS-dan members was commanding a space fleet, and each of them was shown in a bridge filled with BridgeBunnies of their own imagining (ItMakesSenseInContext). Mikuru's crew (a bunch of stuffed animals) were lifted from doodles that Creator/AyaHirano (Haruhi's seiyuu and occasional {{Cloudcuckoolander}}) had drawn in the margin of her scripts.
** When Kyon first meets the future version of Mikuru, she tries to prove who she is by showing him a star-shaped mole on her breast, and he stumbles back thinking "HUGE!" In the dub, Creator/CrispinFreeman ad-libbed "SUPERSIZE ME!" instead, and everyone thought it was hilarious, so it was kept.
* According to ''TigerAndBunny'''s scriptwriter, Nishida Masafumi, Origami Cyclone's habitual photobombing tendencies were something that he suggested to the producers as a joke. He was surprised that they agreed with the idea.
* In ''Manga/DetectiveConan'', the character Wataru Takagi did not originally exist. He was a nameless character. In one scene, Inspector Megure asks his name and his voice actor (Creator/WataruTakagi) responded with his name. Gosho Aoyama, the mangaka, kept it in.
* On a whim, the artist of ''BusouRenkin'' decided to add a butterfly mask to the BigBad of the first arc. This turns out to be fairly significant, as he is a recurring character, and the butterfly motif drives most of his personality.
* In ''InazumaEleven GO'', Creator/HirofumiNojima ad-libbed a {{Kiai}} as Kurumada, which sounded something like "shupoh!" It has since more or less become Kurumada's trademark exclamation.
* In-universe: Negishi in ''DetroitMetalCity'' (as Krauser) is invited to take part in an indie film by a director who turns out to be a LoonyFan and completely sold by the band's {{kayfabe}}. He also discovers that the female lead is an up-and-coming actress he greatly respects. The climax of the film turns out to be a sex scene the actress doesn't want to do, and Negishi, in order to protect her career, deliberately ruins it by ad-libbing in a physical assault on the male lead before the scene gets anywhere. The director considers the new direction the scene takes to be brilliant and leaves it in as a TwistEnding instead of re-shooting.
* Dub example: John Ratzenberger's little soliloquy about the fat rich customer in ''SpiritedAway''.
* In ''LightNovel/HighSchoolDXD'', it was revealed in the afterword of Volume 12 that Ophis wasn't supposed to join the Occult Research Club group, though the author and his editor liked her design so much that he made her join anyway.
* The soldier who is going to execute Shinji in ''[[Anime/NeonGenesisEvangelion End of Evangelion]]'' was always scripted to say it was NothingPersonal, but as originally directed the line would have come off as bloodthirsty. The voice actor instead read the line in a casual, almost joking, fashion. That version was used, as the result was even more chilling.
** Shinji has no dialogue after [[spoiler: Kaworu's death]] in the third ''Anime/RebuildOfEvangelion'' movie because his voice actress, Creator/MegumiOgata, was too distraught to continue recording her lines. The director thought it worked, so he kept Shinji in a [[HeroicBSOD grief-induced borderline coma]] for the rest of the film.
* Another InUniverse example and played UpToEleven: ''Anime/SmilePrettyCure'''s main cast volunteers to help a director shoot a JidaiGeki film in Episode 33, but there's always someone going OffTheRails in some way: Miyuki says "[[GratuitousEnglish Ultra]] [[CatchPhrase Happy]]!", Akane (playing a literal DemonicSpider) can't help but speak in her KansaiRegionalAccent, Nao is a HighlyVisibleNinja that pretty much has a soccer kick-off contest with Akane to keep Reika who's playing the DamselInDistress. Nao losses, but Pop joins in and challenges Akane to an [[NarmCharm amusingly dramatic]] samurai showdown in which he wins. The other actors are constantly worried [[LampshadeHanging that the script is not being followed at all]] while the director is getting more and more excited as the shot is being taken. See it in all its glory [[http://www.youtube.com/watch?v=vCYSDWDls9A here]].
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