There was always something off about Izuku Midoriya.
He's a Quirkless. Or, as he puts it, he didn't get a christening gift from his parents. Despite this, he wants to be a Hero more than anything. Not just to be like his idol, All Might, but to show half-breeds like him everywhere that they can screw their heritage and that they're just as worthy as everyone else, or at least to convince himself of that.
That isn't to say he doesn't have powers. He's got those, but he keeps them hidden, let's everyone think he's worthless until he's out of middle school. It's better than getting that slashing feeling in his throat from lying about it.
He also gets dreams. Dreams of things to come. Sometimes he's drowning in a pool filled with chlorine. Other times he sees a boy about to be killed by a psychotic murderer in a bloodstained mask. He doesn't know where or when they're going to happen, but they're going to happen if he doesn't do something about them.
After school, he's usually doing jobs for an "acquaintance" of his named Beck. It would be more accurate to call it "indentured servitude", because he doesn't have any say in the matter. He has to do everything Beck asks, all because Izuku didn't know the rules as a child and handed out his True Name to the wrong person.
Another thing he doesn't want anyone to know about him:
He's a fake.
More specifically, he's a changeling. His biological parents swapped him out for the real Izuku Midoriya when they were infants. He's been living Izuku's life ever since. You see, "Izuku" is a faerie, more specifically, the son of a no-name puca woman and an elf of the Seelie Court. He's the forbidden product of a disgraceful affair between fae of different courts. Caught between the worlds of Heroes, Villains and the faeries that lurk just below the surface, Izuku will do his best to achieve his dream and break free of the fae that would seek to put him down for what he is.
Cuckoo Bird is a My Hero Academia Alternate Universe Fanfic written by ElectricBoomerang on Archive of Our Own. In a world where faeries are responsible for the rise of Quirks, the changeling called Izuku will become a Hero while dealing with the supernatural world that exists alongside the already fantastical society he lives in.
It can be read here.
Cuckoo Bird provides examples of:
- Adaptational Early Appearance: Aizawa meets Izuku and works with him for ten months before he goes to U.A. while dealing in fae business to keep the faeries away from the work of Heroes and Villains.
- Mirio Togata appears much earlier in the story as All Might (in his civilian guise as Toshinori Yagi) prepares him to receive One For All while Izuku visits Dagobah Beach to prepare for the U.A. Entrance Exam.
- Adaptational Personality Change: While most of Izuku's Character Tics are intact, he's notably more cynical and coarse in his internal dialogue due to years of wearily doing Beck's bidding.
- Adaptation Species Change: Izuku is a faerie rather than a human.
- Todoroki's mom is a Selkie who goes by Drift, making Shouto half-selkie, though biologically he's just a human with Sight and a Quirk.
- Adaptational Superpower Change: Izuku doesn't get One For All, instead he gets by with his magical abilities, which he passes off as a shapeshifting Quirk.
- All Genes Are Codominant: Subverted. Despite having the blood of both a puca and a pure-blooded elf, Izuku's half-breed status gives him only barebones access to his magical abilities. At the same time, Todoroki is just a human with a Quirk and Sight, rather than a selkie like his eldest brother.
- Animorphism: Izuku's magical abilities allow him to do turn parts of his body into that of animal, allowing him to gain claws and wings. He can also completely turn into a handful of animals, such as a crow, a cat, a dog, a fox, and a goat. Unfortunately, his abilities aren't quite powerful enough to hurt U.A.'s robots, nor do they allow him to bypass his weakness to iron.
- Big Brother Mentor: Mirio is happy to play this role for Izuku. When Izuku tries to leave after mistakenly intruding on Mirio's training session on Dagobah, Mirio just tells him that Izuku was there for longer since it was Mirio's first day here. After that, he and Izuku train by hauling trash off the beach. Mirio is also ecstatic to hear that Izuku passed.
- Blessed with Suck: Izuku's regular abilities, while useful, pale in comparison to a full-blooded elf's and he still suffers from the standard faerie weaknesses to iron and ash trees. His prophetic dreams, which come on "Teeter Days" (the author's original creation), leave him feeling sick and even feverish. He also can't opt out of them and they come whenever they please. Unlike Sir Nighteye's, these aren't set in stone, and Teeter Days are important because a single decision Izuku makes can change the course of the future.
- Boxing Lessons for Superman: Izuku spends several months at Dagobah training for the U.A. Entrance Exam with Mirio's and All Might's guidance. It pays off when he finds that he has just enough physical strength to push the rubble off Uraraka, allowing him to fly her out of the zero-pointer's stomping range and get them safety after Uraraka helps him with her Quirk.
- Cannot Tell a Lie: As a faerie, Izuku cannot tell a lie without getting an excruciating slashing feeling in his throat, causing him to use Metaphorically True statements as much as possible so he doesn't have to call his abilities a "Quirk".
- Changeling Tale: The story is one, as "Izuku" is the changeling that was swapped out for the original Izuku Midoriya as a baby. He feels terrible about this, since he knows he's a "fake". He even says that his own name tastes like ash on his tongue because he knows it wasn't originally his.
- Yet, when he tries to tell the truth to his mom right before taking the U.A. Entrance Exam, she simply tells him that she already knew since she was the one who taught him his Glamour spell when he was a toddler. She then tells him that even if he isn't her biological son, she raised him and loves him with all her heart, and that makes him her son just as much as his "brother" is.
- Creepy Shadowed Undereyes: Years of indentured servitude has given Izuku these, but he's shocked to find that Aizawa has even deeper circles than he does.
- Does Not Know How to Say "Thanks": Izuku doesn't even when he wants to, because it's faux pas among the fae to say thanks instead of offering a gift.
- Dreaming of Things to Come: Izuku frequently has prophetic dreams of what's going to happen in the future on what he calls "Teeter Days", such as being trapped in a pool full of chlorine, seeing one of the Noumus, and seeing Stain attacking Iida, and All Might's retirement. Unlike Sir Nighteye's visions, Izuku can't control when he gets them nor are these visions set in stone. He has to pay special attention on the days that he gets them because a single decision can change the course of fate, which results in a feeling that things are locking into place. Unfortunately, these Teeter Days also give Izuku nausea, fevers, and headaches as a side-effect, which makes it harder for him to pay attention on those days. Worse still, Beck's orders against "spoilers" prevent Izuku from telling others about his dreams, forcing him to work behind the scenes to get a better outcome.
- Experienced Protagonist: Izuku has been dealing with the fae for years because of his careless mistake as a child, giving him in-depth knowledge on how the fae work and operate as well as numerous physical reminders of his previous experiences, such as his ironfire scars and his half-chewed off right ear. He still has a long way to go towards mastering his abilities, since he struggles to sprout wings for flight while trying to save Uraraka, but he already has a plethora of transformations available to him.
- The Fair Folk: The driving force behind the story is the machinations of the fae, which led to the rise of Quirks. Izuku knows that the vast majority of them aren't as friendly as he is and actively has to deal with them because of his indentured servitude to Beck.
- Faux Affably Evil: Beck acts cheerful and friendly, but he's a Chaotic Evil sadist who likes nothing more than to exploit Izuku for all he's worth because Izuku made the mistake of spilling his True Name to Beck as a child. Beck also forces orders and rules on Izuku just to see him squirm and struggle.
- First-Person Smartass: Izuku is this in his internal dialogue, snarking at everything that bugs him.
- Friendless Background: Because he's Quirkless and refuses to use his shapeshifting abilities in public until he's out of junior high, he suffered no end of bullying from Bakugou and his classmates even though Izuku does have powers. The fact that Mirio and All Might (as Toshinori Yagi) were willing to give him the time of day and even help him meant the world to Izuku.
- Glamour: Izuku hides his puca features, like the scales on his arm, his goat ears, the scar on his lip, and his lion-like tail with glamour that he actively has to keep up to look human. Beck forces him to drop it when they're doing business and it also comes apart when he's feeling too distressed to hold the spell together. He drops it himself while using his abilities, making it seem as though he has a shapeshifting Quirk.
- Happily Adopted: Izuku considers Inko his real mom over his biological parents, who left him in the human world to hide their affair while stealing away the original Izuku Midoriya. She treats him with nothing but love and affection even after she reveals that she knew for the longest that Izuku wasn't her biological son and he loves her right back.
- Hero-Worshipper: Izuku still admires All Might for being able to inspire others and giving them a symbol to rally behind, but also because he continues to fight for what he believes in despite being messed up after he got his injury six years ago.
- Hybrid Power: Inverted. Half-breeds like Izuku only have the barebones basics of magical abilities. Izuku himself only has glamour, some shapeshifting, and his prophetic nightmares. Pure-blooded elves like Beck can make things appear out of thin air and teleport.
- I Know Your True Name: The most powerful weapon a faerie has is knowledge of another's True Name, which can force that faerie to do things for the one who knows their name. Because of this, everyone who deals with the fae, from lowly half-breeds like Izuku to the highest members of the Unseelie Court, deal with each other in pseudonyms while taking care not to become so attached to them lest they become their True Names. Izuku has no problems using "Deku" as his pseudonym because of the negative connotations attached to it. As a child, Izuku carelessly told his name to Beck, which has forced him into indentured servitude ever since. Beck also uses this to keep Izuku from telling others about his prophetic dreams, since Beck's "friend" doesn't like "spoilers".
- Even humans with Sight have to follow this same rule. Aizawa uses the pseudonym "Present Mic", his best friend's Hero Name, to make sure he doesn't get attached to it. Because of his admiration for Heroes, Izuku refuses to call Aizawa that, just calling him "Present" instead.
- Izuku himself knows the True Name of a kelpie, Undertow, using it along with a debt to force him to help Izuku find a selkie's sealskin.
- Jerk with a Heart of Gold: Aizawa is stern with Izuku and rarely lets on more than necessary out of a (justified) fear that being too candid would allow the fae to exploit him. Despite this, he offers some backhanded words of encouragement to Izuku after learning that the boy wants to take the U.A. Entrance Exam and become a Hero (which leaves Izuku crying Tears of Joy) and offers to transport the selkie's sealskin back to its original owner for him at no benefit to Aizawa himself.
- The Knights Who Say "Squee!": Izuku is still a Hero Otaku to the nth degree and is squealing like a fangirl inside when he realizes that "Present" is the Underground Hero Eraserhead.
- Kryptonite Factor: Faeries like Izuku burn if they touch iron. Izuku has a scar from his lip to his jaw because of an encounter with someone who used ironfire against him. This also proves to be his undoing during the U.A. Entrance Exam, since he can't even touch any of the robots because they're made of iron. He only manages to pass due to his selfless desire to save Uraraka from the zero-pointer.
- Faeries are also repelled by ash trees, causing Izuku's frustration when he's trying to retrieve a sealskin that's kept in an iron lockbox and wrapped in ash tree roots. Luckily, Aizawa is fully human and has a lockpick.
- Little Bit Beastly: Izuku's true appearance is this along with Mix-and-Match Critters. He has black goat ears (one of which has been half-chewed off) and a black lion's tail on top of scales up and down his arms that change color depending on his mood.
- Living Lie Detector: With the exception of Beck, Izuku prides himself on his ability to read others and know when they're lying and how badly they're lying, having spent years using every conversational trick in the book to avoid getting screwed over by the fae more than he already has. He knows that All Might suffered a severe injury several years ago while watching him on TV and through his dreams. He also knows when Toshinori Yagi is lying to him, but he can't figure out why.
- Magic Pants: Subverted. Like Amajiki, Izuku's shapeshifting abilities wreak havoc on his clothes, tearing his shirt to bits after he sprouts giant wings in order to get Uraraka away from the zero-pointer.
- Metaphorically True: Izuku is a master of telling half-truths out of necessity since he has to avoid actively telling lies, lest he suffers excruciating pain in his throat.
- Missing Mom: Todoroki's mom vanishes from the mental hospital in this story. She's gone into hiding once her sealskin was recovered. She then asks Izuku to bring her eldest son, a selkie, home and look out for her youngest son, Shouto, and to tell Shouto that he can meet with her if he needs to.
- Mixed Ancestry: As mentioned below, Izuku is half-puca and half-elf, which unfortunately grants him only limited perks of being either of them on top of heaps of discrimination by other faeries.
- My Significance Sense Is Tingling: Izuku gets a "click" in the back of his mind when he meets someone who's important to his destiny, though he can never be certain as to how or why. He gets this click around Uraraka, which spurs him to save her from the zero-pointer alongside his existing heroic instincts. He also gets this click around Mirio and Toshinori, which is why he decides to stick around them rather than run away.
- The Nicknamer: When Izuku hasn't learned people's names, he tends to call them by nicknames in his head. Because he knows that Uraraka is important to his destiny for one reason or another, he calls her "Destiny Girl". He also calls Iida "Doomed" because he saw him being attacked and murdered by a Villain.
- Non-Human Humanoid Hybrid: Izuku is the result of the communion between a puca and an elf, causing him to be looked down upon by other fae and diluting his magical abilities.
- Older Than They Look: Beck looks close to Izuku's age, but given the nature of the Fae, Izuku has no way of actually knowing how old Beck is. It doesn't help that Beck also attends U.A. as a General Education student to get cozy with the elite members of human society.
- Pro-Human Transhuman: Izuku is a faerie but he actively looks up to and admires human Heroes like All Might and wants to be like them.
- Scars Are Forever: Izuku still has burn scars on his shoulders and arms from the times Bakugou used his Explosion Quirk on him as well as an ironfire scar on his face and a half-chewed off right ear.
- Selkies and Wereseals: Todoroki's mother is a selkie, as is her oldest son.
- Shapeshifting: Izuku can use his magical abilities to turn his body parts into that of animals or completely transform into a handful of animals. He can also turn his scales to stone for improved defense among other things. He's still not used to all of his transformations though and struggles when he has to sprout wings from his back in order to save Uraraka simply because human-shaped creatures aren't meant to fly with bird wings.
- Tears of Joy: Izuku is brought to tears when he hears Mirio and Toshinori tell him that he'd make a great Hero. He's even more happy when Aizawa tells him that he expects Izuku to be at the U.A. Entrance Exam and that his chances weren't zero. He does so another time after his mom reveals to him that she knows that he's a changeling and while she misses her original son, she considers Izuku her son just as much as his whisked away "brother".
- True Sight: Aizawa has this, which has led him to make deals with the fae to keep them as far removed from the human world as possible and bumping into Izuku earlier than in canon.
- Todoroki has this as well through his mother, a selkie.
- Wrong Context Magic: The modern world mistakenly believes that Quirks are just a natural part of evolution. In reality, they're magic "christening gifts" that lay dormant in the blood of humans because of the affairs and trickery of the fae.