Undertale Crossovers
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Determined Magic by the Neutrals reviews
What happens when a child that has never known a true family finally discovered one in the most unlikely of places what lengths will he go to save them? The future is unclear but one thing is certain he is filled with determination. Monster Frisk. Harry Potter is Frisk.
Crossover - Harry Potter & Undertale - Rated: M - English - Family/Hurt/Comfort - Chapters: 6 - Words: 25,331 - Reviews: 12 - Favs: 31 - Follows: 32 - Updated: 1/14 - Published: 11/16/2021 - Harry P., Asriel, Toriel, Asgore D.
Willoughby Madness! by callofdutyFTWnintendoFTL
Join this fanfic through an epic journey, the adventures of the wacky Principal Willoughby, on his quests to get what he wants!
Crossover - Jimmy Neutron & Undertale - Rated: M - English - Adventure/Sci-Fi - Chapters: 1 - Words: 2,328 - Published: 1/12 - Principal Willoughby, Asriel, Papyrus, Sans - Complete
Monstrous Heroes by Wistful Mindscape reviews
The whole of City Z shook as a mysterious house appeared in the street. Little did they and their protector Saitama know that these new visitors would bring destruction, hope and determination. Pacifist ending. SPOILERS FOR BOTH SOURCES
Crossover - One Punch Man/ワンパンマン & Undertale - Rated: T - English - Humor/Adventure - Chapters: 16 - Words: 71,511 - Reviews: 139 - Favs: 270 - Follows: 291 - Updated: 1/7 - Published: 10/28/2016 - Saitama, Papyrus, Sans
MEGA PIZZAPLEX ARCHIVES - FILE 01 by Kraxicorde reviews
Wel-Welcome to Fre-Freddy Fazbear's Mega Pizzaplex! This massive attraction boasts of being our most ambitious project yet, with top-notch security and [UNABLE TO READ DATA]! Come play at this safe* multiplex for all ages! *Disclaimer- The Pizzaplex cannot guarantee guest safety. It is [UNABLE TO READ DATA] never to stay after dark.
Crossover - Five Nights at Freddy´s & Undertale - Rated: T - English - Adventure/Horror - Chapters: 2 - Words: 2,214 - Reviews: 2 - Favs: 8 - Follows: 11 - Published: 1/5 - Glamrock Freddy, Gregory, Frisk, Sans
A Reset Gone Wrong (Rewritten) by I'dMakeANameButIDon'tWantTo reviews
After finally winning, Sans, using his new human soul, uses his powers to Reset. But, unfortunately for Sans, his attempt to Reset the world results in highly unexpected events.
Crossover - RWBY & Undertale - Rated: M - English - Chapters: 5 - Words: 36,927 - Reviews: 28 - Favs: 71 - Follows: 97 - Updated: 1/4 - Published: 4/19/2020
Anomaly Between Worlds (a Food Fantasy isekai fanfiction) by Danny RPG NineTwoOak reviews
Due to character limits, I'll keep it simple: This is a first-person isekai story where my avatar (an alternate version of myself) gets trapped in the world of Food Fantasy and tries to adapt to her new life. For more details, see me on Instagram, DeviantArt, and Wattpad.
Crossover - Food Fantasy & Undertale - Rated: M - English - Humor/Adventure - Chapters: 17 - Words: 53,415 - Reviews: 2 - Favs: 6 - Follows: 5 - Updated: 1/4 - Published: 12/11/2019
Promise by roguestar23
After the traumatic events she experienced in the Underground, Monika has finally gotten her happy ending with the player. However, it came with a promise not to mess with any of the other girls. But when strange things start happening, she's worried that she might not be able to keep that promise. A sequel to Monika Visits the Underground, please read that first if you haven't.
Crossover - Undertale & Doki Doki Literature Club - Rated: T - English - Friendship/Hurt/Comfort - Chapters: 8 - Words: 7,279 - Favs: 4 - Follows: 3 - Updated: 1/4 - Published: 11/14/2021 - [OC, Monika] Chara - Complete
Knights, Warriors, and a Judge (Migrated) by WhoWantsAWaffle reviews
All it takes is the random appearance of two characters from a completely different universe to offset the path fate has set for a certain virtual world. Sans and Undyne in an AU where the Central Cathedral raid fails. (Along with possibly the most uncanon ship in all of SAO and Eugeo x Alice)
Crossover - Sword Art Online/ソードアート・オンライン & Undertale - Rated: T - English - Fantasy/Supernatural - Chapters: 12 - Words: 35,617 - Reviews: 1 - Favs: 12 - Follows: 17 - Updated: 1/3 - Published: 12/15/2021 - [Kirito/Kazuto K., Yuuki/Yuuki K.] Sans, Undyne
Hopes, Dreams, And DELTARUNE, Book 1: The Dark World by Dragonsrule18 reviews
In one world, a neglected girl searching for a flower for a professor to make money to take care of her sister fell into a world full of monsters and freed them. But in the timeline just to the left, the war never began. But Frisk's fate is still tied to the monsters, and a transfer to a new school leads her and fellow outcast Susie to a new world. A Dark World.
Crossover - Undertale & Deltarune - Rated: T - English - Friendship/Adventure - Chapters: 7 - Words: 48,305 - Reviews: 32 - Favs: 23 - Follows: 18 - Updated: 1/1 - Published: 11/20/2021 - Frisk, Lancer, Ralsei, Susie - Complete
Ruby Red Eyes by DazMaZ reviews
The war of Heroes and Villians rages on, but what happens when DETERMINATION appears in their world?
Crossover - My Hero Academia/僕のヒーローアカデミア & Undertale - Rated: T - English - Adventure/Friendship - Chapters: 7 - Words: 42,319 - Reviews: 104 - Favs: 316 - Follows: 410 - Updated: 12/30/2021 - Published: 8/28/2020 - Katsuki B., Frisk, Chara
Alfheimtale by CrumpsCrumbs
It's Papyrus's birthday, and his brother got him a copy of Alfheim Online! In this magical world, he meets many new people, including Kirito and his friends, but things take an unexpected turn when they meet a mysterious person. Will Kirito and Papyrus see eye to eye before they lose everything? Or will the line between friends and enemies be destroyed before they can?
Crossover - Sword Art Online/ソードアート・オンライン & Undertale - Rated: T - English - Adventure/Friendship - Chapters: 12 - Words: 23,981 - Favs: 1 - Follows: 1 - Published: 12/28/2021 - Kirito/Kazuto K., Asuna/Asuna Y., Klein/Ryoutarou T., Papyrus - Complete
Alice in Undertale by Lolitafreak88 reviews
What if by some curious opportunity, instead of Wonderland... it was the Underground, the realm of monsters that Alice fell down the rabbit hole into? It's a world just as curious, with as many colorful characters, and things to discover... but is 'kill or be killed', 'mercy or violence', 'a good time or a bad time'. Can her curiosity and imagination open up into determination?
Crossover - Alice in Wonderland & Undertale - Rated: T - English - Friendship/Fantasy - Chapters: 41 - Words: 349,575 - Reviews: 283 - Favs: 268 - Follows: 256 - Updated: 12/27/2021 - Published: 11/6/2015 - Sans, Chara, Toriel, Flowey
Alphys sick days by Idontknow2034
Holaa, en esta historia Aphys esta enferma, Undyne les dice a sus amigos para cuidarla, a los que todos aceptan, esta historia sera de 10/15 capitulos, espero que lo disfruten! Igual abra un Crossover!
Crossover - Undertale & Squid Game - Rated: K - Spanish - Romance - Chapters: 9 - Words: 1,466 - Updated: 12/24/2021 - Published: 10/30/2021 - [Alphys, Undyne, Ji-yeong, Kang Sae-byeok]
Chloétale by SwapAUAnon reviews
Falling into a world of monsters was not how Chloé planned on spending her retreat, but if she can just make her way through the cavernous Underground, she might just survive. Eventually. There's plenty of LOVE to go round, after all.
Crossover - Miraculous: Tales of Ladybug & Cat Noir & Undertale - Rated: T - English - Hurt/Comfort/Friendship - Chapters: 2 - Words: 4,368 - Reviews: 7 - Favs: 6 - Follows: 5 - Updated: 12/22/2021 - Published: 11/5/2021 - Chloé B./Antibug
Re:zero Sans by Lemonman12 reviews
It's the story of Re:zero except Subaru Natsuki has Sans Undertale power's. He will follow a similar story line with a few changes ;).
Crossover - Re:Zero & Undertale - Rated: K+ - English - Friendship/Adventure - Chapters: 15 - Words: 37,314 - Reviews: 6 - Favs: 30 - Follows: 33 - Updated: 12/19/2021 - Published: 12/14/2021 - Subaru N., Rem, Beatrice, Sans
Selection Error by WingedSword reviews
The Vytal Festival, where teams of huntsmen and huntresses from across Remnant would assemble to battle and show their prowess as proud huntsmen. The first match of the Festival was supposed to be Team RWBY facing Team ABRN of Haven Academy… but the team matchup bugged and the world glitched. Cover Art by me, One shot story.
Crossover - RWBY & Undertale - Rated: T - English - Supernatural/Mystery - Chapters: 1 - Words: 3,913 - Reviews: 2 - Favs: 13 - Follows: 9 - Published: 12/19/2021 - Team RWBY, Gaster - Complete
The HATE-filled Huntress by mamamimikyu64 reviews
What if Ruby wasn't the fun-loving, innocent Huntress we all know? What if she wasn't Human, Faunus, or even Grimm? What if Ruby Rose was the personification of malice itself? (Glitchtale Crossover)
Crossover - RWBY & Undertale - Rated: T - English - Family/Fantasy - Chapters: 1 - Words: 1,179 - Reviews: 4 - Favs: 19 - Follows: 22 - Published: 12/18/2021
The Black Beast by mamamimikyu64 reviews
What if Izuku had a Quirk? What if it awakened when he was four? What if the reason for it surfacing was the murder of his mother? What if he became a hero more terrifying than the villains? (Glitchtale Crossover) (Rated M for graphic descriptions of injuries)
Crossover - My Hero Academia/僕のヒーローアカデミア & Undertale - Rated: M - English - Humor/Crime - Chapters: 1 - Words: 611 - Reviews: 2 - Favs: 24 - Follows: 34 - Published: 12/16/2021
Under the Veil by poplasia reviews
Sans has gotten himself stuck in the void between worlds in a successful attempt to stop the resets of his timeline. He's not sure how long he's been chillin' alone there, but eventually a chance at escape stumbles his way in from the Veil of Death. His name?—Sirius Black. (no pairings)
Crossover - Harry Potter & Undertale - Rated: T - English - Fantasy/Humor - Chapters: 62 - Words: 214,115 - Reviews: 2091 - Favs: 2,112 - Follows: 2,424 - Updated: 12/13/2021 - Published: 8/1/2016 - Sirius B., Sans
Loudtale Orange by AP100 reviews
The story of a universe made of Loud House and Undertale blended together.
Crossover - Undertale & Loud House - Rated: T - English - Supernatural/Adventure - Chapters: 7 - Words: 35,339 - Reviews: 4 - Favs: 2 - Follows: 3 - Updated: 12/13/2021 - Published: 10/12/2020
Batmantale by AlithiaSigma reviews
Batman finds himself in the Underground with nothing but his clothes and the drive to continue on. Really, it's Batman in Undertale. And Batman does have one power. He never gives up.
Crossover - Batman & Undertale - Rated: T - English - Chapters: 8 - Words: 14,386 - Reviews: 114 - Favs: 121 - Follows: 182 - Updated: 12/13/2021 - Published: 2/21/2016 - Bruce W./Batman, Sans
Wind and Fire by Redwood Sorrow reviews
The Avatar has the greatest power of all. Determination. The ability to persist through even the most trying of circumstances. But with the weight of the world on his shoulders, and an equally determined princess after him, will it be enough to restore balance?
Crossover - Avatar: Last Airbender & Undertale - Rated: T - English - Adventure/Drama - Chapters: 30 - Words: 166,417 - Reviews: 41 - Favs: 35 - Follows: 42 - Updated: 12/11/2021 - Published: 4/7/2018 - [Aang, Azula] Katara, Frisk
Un monde vraiment parfait (DBS x X-Tale) by FataliseMH4
Pendant le tournois du pouvoir, un être avec le pouvoir de réécrire et de reset le multivers viendra
Crossover - Undertale & Dragon Ball Super - Rated: T - French - Mystery/Supernatural - Chapters: 1 - Words: 559 - Published: 12/11/2021 - Gaster - Complete
Crimson Hunt by TheOriginalTale reviews
When a hiking accident sends Frisk to the depths of Mount Ebott, he's forced to adapt to his new surroundings. Meanwhile a restless prince seeks for adventure...and a new visitor just might provide the means to fulfill his cravings.
Crossover - Undertale & Deltarune - Rated: T - English - Adventure/Fantasy - Chapters: 14 - Words: 26,884 - Reviews: 2 - Favs: 6 - Follows: 10 - Updated: 12/7/2021 - Published: 9/28/2021
Undertale X Mha (My hero academia) by Black. cat.002 reviews
The title says it all. Sans goes to Mha. There you go. I might be lazy. Won't upload quickly. #lazyauthorchan ...anyway, this is a almost no logic story but if you can bear with it, I'll thank you a lot. Lol
Crossover - Undertale & My Hero Academia/僕のヒーローアカデミア - Rated: K - English - Adventure/Crime - Chapters: 7 - Words: 4,336 - Reviews: 9 - Favs: 7 - Follows: 9 - Published: 12/7/2021 - Sans, 1-A Students
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