History SmallRoleBigImpact / AnimeAndManga

** Dr. Gero. He's long dead in Trunks' timeline and is only around for a few episodes as Android 20 before being killed by Android 17. However, it is Gero who created all the androids, including Cell, and his actions turns two timelines into a living hell and nearly destroys the solar system of the main timeline. Literally ''everything'' bad that happens in the Android/Cell Saga is his fault.

** The Chainsaw Nomu that appears in the Training Camp arc, chases Yaoyorozu and Awase around a bit, and then leaves. But before he does, the two are able to attach a tracking device to him, leading the heroes right to the Nomu Factory, which in turn sets up events with ramifications throughout the rest of the story.

** A minor Marine character named Shu who, despite appearing in only one episode of the anime, managed to actually destroy one of [[MasterSwordsman Zoro's]] swords thanks to his Rust-Rust Fruit powers. Not only did he rust up the sword that Zoro personally received from a man who respected him, but Zoro ends up using two swords for awhile until he finally gets a permanent replacement in the middle of the Thriller Bark arc.

** Sora Vinsmoke is a minor character from the North Blue who's long dead by the time of the story and only interacts with one of the main characters. But her actions indirectly saved the Straw Hats several times over. [[spoiler:She's Sanji's mother, if she hadn't taken a dangerous drug to reverse the gene surgery on Sanji, he would have turned out like his brothers -- superpowerful, but completely lacking in empathy and would never have joined the Straw Hats.]]

** The lives of the protagonists of Parts 4 and 5 were each greatly influenced by an unnamed person who only appears as a part of their flashback, whose face isn't even properly seen.

*** Similarly in Part 5, Polpo appears in only two scenes (''his own stand'' has more page-time than him), but his death drives the plot just as much as Luka's, both in the revelation that he had a massive treasure hoard hidden away (that Bucciarati uses to boost themselves to Operator status) and the revelation that he was responsible for protecting Trish, the daughter of TheDon of Passione. After his death, Bucciarati and his team are tasked with protecting Trish.

** Sora Vinsmoke is a minor character from the North Blue who's long dead by the time of the story and only interacts with one of the main characters. But her actions indirectly saved the Straw Hats several times over. [[spoiler: She's Sanji's mother, if she hadn't taken a dangerous drug to reverse the gene surgery on Sanji, he would have turned out like his brothers -- superpowerful, but completely lacking in empathy and would never have joined the Straw Hats.]]

* Dying Breed rarely appear in ''Manga/{{BECK}}'', but they inspire both Ryuusuke and Koyuki to push the band to great heights, and [[spoiler: Eddie Lee's death]] causes a HeroicBSOD from almost the entire music world. Not only that, but rumors of an unreleased song of theirs drive a huge portion of the plot.

* ''Franchise/KagerouProject'': Tsukihiko, Azami's husband, appears very briefly in the anime, and in only one of the music [=PVs=], yet his love and acceptance of Azami was what led her to develop her own emotions, resulting in the creation of the Heat Haze World and [[spoiler:the [[EmotionBomb Favouring Eyes Snake]], born of her love for her husband and child, and [[ForWantOfANail the snake that is the key to saving everyone]]]]. Azami herself could count, as she is the source of the main cast's powers [[spoiler:and the grandmother of Marry]], and she appears nearly as little as her husband does.

** Doctor Tsubasa can be considered this for being the one to tell Midoriya that he doesn't have a quirk, and thus drastically affect Midoriya's life, views, and relationships from that point onward. 'Can be' being the key word, as a doctor looking very much like him was shown [[spoiler: as All for One's physician]], up to sharing voice actors, leaving it ambiguous just how small his role in the story is.

** Mizuki is an extremely minor villain that only appears in the first chapter and permanently disappears from the manga afterwards, but were it not for him, Naruto would've never taken the Scroll of Seals from which he learned the Shadow Clone technique, which he uses throughout the series.

** [[EasternZodiac The Horse Deva]], Indramon, only appeared in two episodes, the second of which was his death. However, his vicious beatdown on Impmon set in motion the events that led to Impmon making a deal with the Devas to become Beezlemon.

** [[spoiler:Kyojuro]] is the first Hashira the main trio are officially drafted on a mission with. [[spoiler:Kyojuro dies on that same mission, but he]] leaves quite the impression on Tanjiro, as a mentor figure and friend; [[spoiler:Kyojuro's flaming determination became a part of Tanjiro quite literally, as Kyojuro's original sword guard was preserved and then embedded on Tanjiro's fourth sword in the series. Kyojuro's death is also the first one Inosuke reacts to with proper sorrow.]]

** [[spoiler:Van Hohenheim's master, as well as the King of Xerxes]] are already long dead by the time the story begins[[note]]And in the latter's case, he is only brought back to life in an [[BodyHorror unstable body]] [[BackForTheDead before Father kills him]].[[/note]] and [[NoNameGiven aren't even given names]], but they both play an important role in the backstory of [[BigGood Hohenheim]] and [[BigBad Father]] that would set the plot in motion. [[spoiler:Hohenheim's master and alchemy teacher would create the homunculus that would become Father from Hohenheim's blood, and the King of Xerxes, in his desperation for immortality, would be manipulated by the homunculus into creating a transmutation circle that would sacrifice the population of Xerxes and trap their souls within Hohenheim and the homunculus, granting them immortality and also allowing the latter to create a body for himself that looks identical to Hohenheim]].

* ''Jujutsu Kaisen'':

* Setsuko Sasaki, the president of the fledging Occult Club of Yuji Itadori's school in ''Manga/JujutsuKaisen'' may have vanished from the plot after the Introduction Arc, but her attempting to unseal one of Sukuna's fingers is what kickstarted the plot.

** [[spoiler:Muzan's doctor from the Heian Period created an experimental elixir that could theoretically cure Muzan's terminal illness, but the latter kills him in a fit of anger and impatience when it didn't appear to work. The elixir worked after all and turned Muzan into the first demon, but because he killed the doctor before the treatment could be properly finished, Muzan was left with a [[WeakendByTheLight crippling weakness to sunlight]], leading him to search for the means to overcome his weakness. Despite only appearing for one scene in Muzan's backstory, the entire plot of the series would never have happened if the doctor had not given Muzan the elixir in the first place.]]

** [[spoiler:Van Hohenheim's master, as well as the King of Xerxes]] are already long dead by the time the story begins[[note]]And in the latter's case, he is only brought back to life in an [[BodyHorror unstable body]] [[BackForTheDead before Father kills him]].[[/note]], but they both play an important role in the backstory of [[BigGood Hohenheim]] and [[BigBad Father]] that would set the plot in motion. [[spoiler:Hohenheim's master and alchemy teacher would create the homunculus that would become Father from Hohenheim's blood, and the King of Xerxes, in his desperation for immortality, would be manipulated by the homunculus into creating a transmutation circle that would sacrifice the population of Xerxes and trap their souls within Hohenheim and the homunculus, granting them immortality and also allowing the latter to create a body for himself that looks identical to Hohenheim]].

* ''Manga/TakeResponsibilityForMyStomach'' has Ritsu and Ruka's kohai from the track and field team. The two [[NoNameGiven are never given names]] and [[LastEpisodeNewCharacter only appear in the final chapter]], but their decision to visit their [[SenpaiKohai sempais]] at college prompts Ruka to lose weight for the sake of her dignity, thereby helping establish the SeriesGoal.

* ''Manga/ChainsawMan'': Himeno is a supporting character who [[spoiler:dies about a quarter-way into Part 1]], but her character casts a huge shadow over the rest of the story. Aside from [[spoiler: her death establishing very firmly that nobody in the cast is safe and off-limits (a fact that'd have major repercussions in Part 1's closing arcs), Aki's discovery that she cared enough about him to trade her life for his shocks him out of the self-destructive funk that he's in at the beginning of the story and causes him to start opening up to others and take on a protective mentor role for Denji and Power for others the way Himeno once did for him.]]

* ''Literature/ArifuretaFromCommonplaceToWorldsStrongest'': Aiko's apperances in the light novel can be counted on one hand, yet it's because of her that Hajime went from being from a very selfish anti-hero into someone willing to help others to avoid living "a lonely life".

* ''Literature/BeingAbleToEditSkillsInAnotherWorldIGainedOpWaifus'':
** The Dark Elf mother and her child only appear very briefly in the manga, but it's only because Rita stopped the caravan in order to help them that Nagi learned about the Leviathan in the first place.
** Astarte shows up at the start of the story, guides Nagi to Cecil, and then is never seen or heard again once Nagi buys her. Yet if it had stayed silent, Nagi's prospects in this new world would have been quite grim, and Cecil would still be a "useless Dark Elf" slave, waiting for death in a cell.

* In ''Literature/DeathMarchToTheParallelWorldRhapsody'', Hikaru, the programmer that disappears before the story begins. Without Hikaru helping, [[TheHero Ichiro Suzuki]] is forced to do a programming "Death March" of 80+ work weeks to meet a deadline to finish a game. When he finishes and falls asleep, the next he knows is that he has been returned to his 15-year-old body and sent to the fantasy world where the entire story takes place.

* ''Literature/InvadersOfTheRokujyouma'': Yuuichirou Satomi, Koutarou's father, doesn't appear often, but it's only because Koutarou wanted to lessen his father's burden following his mother's death that he moved into Room 106 and met the girls in the first place. This leads to events up to and including the ''creation of the Universe''.

* ''Literature/MyNextLifeAsAVillainessAllRoutesLeadToDoom'': Baron Shelley only shows up in flashbacks involving Anne, and nothing he ever does directly affects any members of the primary game cast, but him sending Anne to be with the Claes family after effectively disowning her was how she and Catarina become such close friends and she started breaking out of her submissive shell, and Catarina's efforts to stop him from marrying her off against her will is the major push that truly allowed Anne to break free of her mental shackles and decide to be her own person instead of what would potentially please other people.

* ''Literature/RollOverAndDie'': The black market slave merchant appeared in only the first two chapters of the light novel, but the impact he has is immense. If it wasn't for him, Jean would not have had the opportunity to sell Flum into slavery. This causes the Hero's party to start to break apart due to Flum being TheHeart of the party and Jean being short sighted. Additionally, this leads to Flum discovering the true nature of her affinity Reversal, and she also meets Milkit along with beginning her own Hero's journey.
* ''Manga/SaintSeiya'': Sagitta Ptolemy is just another Silver Saint who shows up for a few minutes and easily dies at the hands of Seiya. But not before he embeds one of his arrows in Saori/Athena's heart, giving her only 12 hours to live unless someone shines the light of her shield on her. It so happens that the shield is located at the top of the Sanctuary and Saori's Bronze Saints have to fight the phenomenally powerful Gold Saints to get to it. That's '''30-plus episodes''' of struggling that never would've happened had the mook Ptolemy not done what he did, as the Gold Saints would have just stood to attention if they had met Saori.
* ''Literature/SwordArtOnline'':
** Vassago Casals/[=PoH=]. He has very little screentime in Aincrad compared to Akihiko Kayaba but his actions have an impact that extends far beyond him. [[spoiler:Him establishing the PlayerKilling guild Laughing Coffin and corrupting many a player into becoming player killers and even real-life {{serial killer}}s is what directly causes the Phantom Bullet and Alicization arcs.]]
** Atsushi Kanamoto/Johnny Black. He's a minor but named member of Laughing Coffin, and later plays a small role in Phantom Bullet, [[spoiler:since the Shinkawa brothers needed an additional accomplice to carry out the murders on the day of [=BoB=].]] However, his real impact comes at the start of the Alicization arc, in which he [[spoiler:injects Kirito with his succhyoline, forcing him to be hooked up to the STL and essentially causing the storyline to happen.]]

** The Rare Hunter doesn't even have a name and is in-universe considered a little more than a mook that Yugi effortlessly defeats but it was his defeat of Jonouchi/Joey that demonstrated how dangerous the Ghouls/Rare Hunters were and they have ''much'' better access to rare cards. He also serves to help kick off Jonouchi's arc by showing the gap between him and Yugi and sets Jonouchi off to improve himself. Also, because Yugi won back Jonouchi's Red Eyes Black Dragon from the Rare Hunter and Jonouchi refused to take it back until he became a worthy duelist, Yugi would be able to use the Red Eyes in his later duel to awaken the brainwashed Jonouchi.

* Ai Hoshino from ''Manga/OshiNoKo''; despite being [[AdvertisedExtra the face of the series in promotional materials]], her children Aqua and Ruby are the real main characters, and [[spoiler:she's only around for the first nine chapters of the manga and the first episode of the anime, after which she's murdered. However, her presence still hangs over the rest of the narrative, and finding the man who organized her death is Aqua's primary motivation]].

* The "Ordinary Woman" (or "Ippan Josei" in Japanese), is a minor character with a Mutant Quirk that makes her nearly 10 feet tall and resembles a mix between a shark and fox. She is introduced late in the series with at least 3 chapters and a couple of cameo appearances under her, when hero morale has hit an all-time low and villains have been broken out of prison. While FantasticRacism against "Heteromorphs" has been an ongoing discussion in the series and sometimes in varying degrees, her role as a victim of and unexpected player against it leaves a big impact in some fashion.
** Support for heroes gets so bad, she was attacked by vigilantes who took matters into their own hands but mistake her for a villain herself, blaming her heteromorph appearance when Midoriya steps in to save her. He asks All Might to take her to a nearby shelter, but she is among the others that have been turned away by many because of their appearance. When she is let into U.A, she meets Deku again and thanks him for what he did for her.
** [[Spoiler: During the final battle throughout Japan, when members of the Paranormal Liberation Front send a message out to all heteromorphs to form an attack mob led by Spinner at a hospital, she passes this message along students Shoji and Koda who join teachers Aizawa and Yamada to help stop it. While it was revealed to be a scheme to free League of Villains' Kurogiri, Shoji (who had suffered his own form of racism years ago) wants to stop it before it makes people's view of all Heteromorphs even worse.]]

* ''LightNovel/BeingAbleToEditSkillsInAnotherWorldIGainedOpWaifus'':

* In ''LightNovel/DeathMarchToTheParallelWorldRhapsody'', Hikaru, the programmer that disappears before the story begins. Without Hikaru helping, [[TheHero Ichiro Suzuki]] is forced to do a programming "Death March" of 80+ work weeks to meet a deadline to finish a game. When he finishes and falls asleep, the next he knows is that he has been returned to his 15-year-old body and sent to the fantasy world where the entire story takes place.

* ''LightNovel/MyNextLifeAsAVillainessAllRoutesLeadToDoom'': Baron Shelley only shows up in flashbacks involving Anne, and nothing he ever does directly affects any members of the primary game cast, but him sending Anne to be with the Claes family after effectively disowning her was how she and Catarina become such close friends and she started breaking out of her submissive shell, and Catarina's efforts to stop him from marrying her off against her will is the major push that truly allowed Anne to break free of her mental shackles and decide to be her own person instead of what would potentially please other people.

* ''LightNovel/RollOverAndDie'': The black market slave merchant appeared in only the first two chapters of the light novel, but the impact he has is immense. If it wasn't for him, Jean would not have had the opportunity to sell Flum into slavery. This causes the Hero's party to start to break apart due to Flum being TheHeart of the party and Jean being short sighted. Additionally, this leads to Flum discovering the true nature of her affinity Reversal, and she also meets Milkit along with beginning her own Hero's journey.

* ''LightNovel/SwordArtOnline'':