Author's Note: This is my second submission for B_O_M_B and stop_hunting_me's "The Boy Who Cried Wolf" fanfic challenge. This fics are all set in different universes. Last time was angst, this time I'll do a crack take! Thank you to Goofy_Boss for this awesome prompt.

FYI there are no romantic pairings because I decided to leave adult Izuku's partner ambiguous. That way the reader can insert their favorite pairing. Or alternatively, you can imagine whoever you hate the most getting stuck as All for One's parent.

All Might gazed up at the floating child All for One as he prepared for battle. His mortal enemy looked so small and frail wearing rags, but his evil smirk remained. All Might braced himself for the fight of his entire hero career, where the stakes had never been higher—

A green-haired man popped into existence hovering between them. As soon as he grabbed All for One's head, the villain stopped deaging. He scolded, "Hisashi Midoriya, how dare you run away from home? You have no idea how worried we've all been."

All for One gaped. "I-Izuku Midoriya?"

Now the villain said it, All Might suddenly saw the resemblance. The man looked like an adult Izuku, with the same green curls and freckles. Oddly, he wore a green robe. Was this a trick by U.A.? All Might remained still, not wanting to disrupt the illusion.

Izuku growled, "You are in a world of trouble, young man." He dragged the small All for One into a swirling hole in the air. Then they both were gone.

All Might gaped, his muscles tense, still trying to figure out if he would need to fight. "What…just happened?"

What in the name of quirks had just happened? One second, All for One had been making his final play for control of Japan in his fated last battle with his archnemesis. The next, a giant version of his son had yanked him by his ear into a strange place. This looked like a tower room. Blue sky peeked through the tall windows. A complicated circle surrounded by runes had been drawn on the floor.

The large Izuku scolded, "Other universes are dangerous. Did you see that weirdo wearing the glowing knight's armor? You could have gotten seriously hurt, Hisashi." He yanked the smaller boy into a hug. "Don't scare me like that." As Izuku ruffled his white curls, a blue spark danced from his fingers. "You're grounded. That means no magic and no comic books for the next month."

All for One's brain had yet to catch up with this turn of events, but he had a limited window of time to reach Tomura. How had Izuku gotten older? Maybe he'd started stealing powers like his father? Izuku had referred to him as Hisashi, aka the alias All for One had used when he'd married Inko Midoriya. That meant his rebellious son knew of their relation. How? All for One had carefully and cleanly cut off all ties after All Might had gotten too close to his family.

If Izuku knew, and he'd come to save All for One from All Might, then did that mean Izuku had sided with his father? All for One's heart overflowed with warmth. He'd always assumed his son would abandon him for heroism just like his brother. This was absolutely wonderful news. All for One said, "Ducky, I need you to open another portal to Tomura Shigaraki."

"Who?" Izuku gaped. "Is this another of your silly games?"

The perplexity on his face didn't seem fake. All for One looked around. The round walls of this tower held tapestries of dragons and shelves of colorful bottles. As a long-time fan of isekai comic books, All for One was developing a very bad feeling. Turning back to Izuku, All for One slowly asked, "Are you the ninth holder of One for All?"

Izuku rolled his eyes. "What an imagination you have. There's always another creative story. I'll play later, Hisashi. We need to get you into a bath." His nose wrinkled. "You smell!"

"Wait!" All for One yelped as his own son levitated him up into the air with a wave of his hand. Magic? How fascinating! All for One would be amazed if he wasn't too annoyed at being manhandled by his own child. "Listen, I'm not from your universe—"

"I'm not in the mood for your stories right now." Izuku opened another portal and popped them into a giant bathroom. The bath was truly luxurious, large enough to fit half a dozen people and supported by marble pillars. With another odd hand gesture, Izuku caused steam to rise off the water and lavender scent to fill the air. Then Izuku ripped off All for One's ragged clothes and plunked him into the water.

All for One yelped. The water felt warm—perhaps a little too hot. Mostly he felt annoyed at being pushed around. His current body was only five or six years old. He had no ability to fight back against the adult strength grabbing his arms and scrubbing them.

"Stop that!" All for One tried to use a quirk to propel himself away. Nothing happened. His shock turned to horror. "What did you do to me?"

"I placed a seal on you when I touched your head," Izuku said. "No magic for a month. Not after you nearly got yourself killed with your games. You're lucky I don't make the punishment longer. I will, if you keep talking back." Izuku started washing All for One's hair.

Why did it work on quirks too? Of all the bad luck! All for One sputtered, a bit of soap getting into his mouth. "Stop! I'm not who you think I am. Err. Who do you think I am?"

Izuku sighed deeply as he rubbed in the shampoo. "I'm not playing this game with you."

What did that mean? "I'm not from your world."

"Oh really, kiddo?" Izuku's tone turned joking. "What are you this time? A ninja? A long-lost heir to an ancient kingdom? A dragon hatchling seeking his real parents? That one hurt my feelings a bit, you know. Why are you so eager to find another set of parents when you have a cool father like me, the head of the White Magicians' Order?"

All for One paled as he digested the meaning of this. He'd been transported to a universe where Izuku was his father? Their natural positions as father and son had been reversed? He shuddered in horror at this abomination of younger relatives overthrowing older ones. "You've made a mistake. I'm not your son. I'm a powerful villain in the middle of battling with my rival. It's very important that you bring me back at once. I need to reclaim my brother's ghost from the thieves."

Izuku dumped water over All for One's head. While he sputtered, Izuku said, "Yoichi will be happy he got included in your fantasy games this time."

Yoichi?! All for One's throat suddenly felt dry. His brother was here? Of course his brother must be here. A living little brother. Judging from his own physical age, Yoichi must be even younger than five years old. Still malleable and easily influenced. All for One nearly cackled with glee. He fantasized about taking the small, cute version of his little brother back home with him. "I suppose I can stay long enough to meet Yoichi."

"That's the spirit." Izuku lifted All for One out of the bath and toweled him off, then dressed him in a red and white robe.

"I can dress myself," All for One protested, squirming.

"This is faster, kiddo." Izuku used the magic to wrap the robe on. All for One fumed, convinced he'd never been this overbearing with younger relatives. "There, nice and tidy." Izuku pressed a kiss to the top of All for One's wet head. Some magic must be contained in the kiss, because the water evaporated from his hair.

Then Izuku wrapped a scarf around his neck and put a pointed hat on his head. "You're an adorable little magician."

All for One scowled. "I'm a villain." And he was proud of it.

"Uh-huh," Izuku said indulgently. Unfortunately, All for One recognized that patronizing tone as his own. He did not like it one bit when directed at himself.

A heartbreakingly familiar voice said, "Oh, good. Dad, you found Hisashi."

All for One's head shot up. The door opened. Yoichi wore a pale green robe and a pointed green hat with white stars. He still kept his hair shoulder length and had the same soft green eyes. All for One took a step forward, his arm outstretched longingly. He'd nearly forgotten what his brother looked like as a preteen—

Wait a moment.

Yoichi looked eleven or twelve years old. Ten at the absolute youngest. He definitely towered over All for One, who was currently in the body of a kindergarten.

This was simply impossible. Could Yoichi have used a growth spell? Maybe Izuku would dispel it?

Banishing all hope, Yoichi smiled and said, "I'm glad you're safe. Welcome home, little brother."

All for One toppled over.

Izuku caught him. Yoichi ran over and hugged him. All for One moaned in rejection. He'd longed for Yoichi to hug him willingly for centuries. But not like this! Not as a (gag) older brother! All for One could barely even think the title for the horror. His eyes rolled toward the back of his head.

Distantly, he heard Izuku and Yoichi talking. Yoichi seemed to be saying something about their other parent still traveling worlds looking for Hisashi. Under other circumstances, All for One would have been curious to learn who had presumed themselves worthy to marry his son. At the moment, the horror had overwhelmed him too much to think straight.

"Is he hurt?" Yoichi asked, poking All for One's cheek. "He's never quiet this long."

Izuku flicked a spark at All for One. "I cast a diagnostics spell. He's in perfect health. I think he's just sulking because I took his magic."

"I'm not a magician," All for One insisted. "I'm a villain! A demon king! I have quirks! And I'm the older brother!" He shoved Yoichi. "I refuse to accept this too-large version. Where's my cute baby Yoichi?"

"Still in his lying phase, I see." Yoichi rolled his eyes. "Give it up, squirt. I'll always be older than you no matter how long you live." He ground his fist into All for One's head.

All for One wailed. The tears came as a surprise to him. This younger body might be affecting his mental state. On the other hand, Yoichi being an older brother was horrific enough to make the Symbol of Evil cry.

Izuku batted Yoichi's hand away. "Stop teasing him. Hisashi was very wrong to sneak through my portal and run off. But he's been through a lot. Some strange knight nearly murdered him before I found him." He rocked All for One. "There, there, you're safe now."

All for One gasped. Indignation stopped his tears. "Excuse me? I was about to murder All Might on live television before you interfered me and kidnapped me."

Yoichi rolled his eyes. Izuku said patronizingly, "Sure you were. Because you're a brave little…what was it again? A villain?"

Unfortunately, All for One realized his other self had completely destroyed all his credibility.

Izuku carried All for One downstairs. Carried him! Like a common package! Then Izuku plopped him into a wooden chair. "You must be hungry. I'll make pancakes." The shelves opened on their own. The ingredients floated in the air, mixing together.

To his embarrassment, All for One's stomach growled. Regenerating had taken a lot of energy. But as soon as he ate, he needed to escape this mad mirror world where Yoichi of all people was…he didn't even dare think it. Even fading to nothing in his own world would be preferrable to this horror.

All for One asked, "Um, this portal you used to travel between worlds, where is it located?"

Izuku crossed his arms. "No, Hisashi. Your last escapade gave me a grey hair." He tugged on his curls. "The portal is tightly locked up, and you're under strict supervision."

All for One pouted. "I wasn't trying to run off."

"Yes, you were." Izuku snorted. "You're not a very good liar."

All for One bristled. He was an incredible liar! Only his idiot younger self didn't seem to have any skill in it. Just to prove it, All for One smiled and ate his pancakes like a normal child.

Until Izuku brought out the peas.

All for One glared. "I don't like peas."

"You don't like any vegetables, Hisashi. But you have to eat them if you don't want to be shorter than Yoichi forever."

This was a very convincing argument. All for One shuddered. He'd obtained a quirk to make himself tall, but if his quirks no longer worked, did that mean he had the same shrimp genes as Yoichi?

Tentatively, reminding himself that he'd vowed to act normal, All for One took a bite of peas. Ew! They were too mushy! No one had forced All for One to eat anything he didn't want in a century, not like the early days of his childhood when he'd starved. He pushed away the peas.

"Let's make it a game." Izuku held up a forkful of peas. "Here comes a bird! Can the terrifying dinosaur Hisashi eat it?" He zoomed the fork around in the air.

This was embarrassing. All for One moaned. "Ugh, stop." He got a mouthful of peas in his open mouth. "Hey!"

"You're not leaving the table until you finish your peas," Izuku said in a soft voice covering steel.

Unfortunately, this was not a bluff. He could not escape if he was stuck here in this chair. Slowly, stewing in his downfall from the throne of villainy, All for One ate every last pea.

Then he let Izuku take him to his bedroom, full of stupid children's toys. As soon as the footsteps faded away, All for One ran to the door. He needed to find a set of stairs. The portal had been located somewhere high—

An invisible hand swept All for One back into his room. The door clicked locked. Izuku called, "Nice try. Just for that, you're losing your toys." The wizard dolls and plasticky wands faded away. From behind the door, Izuku said, "I'll let you out for lunch if you behave." In a lower voice, he mumbled, "My beloved was fine with one child, but noooo, I had to have two. Siblings are great friends, I said. Yoichi was an easy child so surely the next one will be too, I said. Ha!"

All for One hated being bored. His early childhood on the streets had largely been exciting, but even a short period of inactivity had usually provoked him to go kill something. He hated staring at his walls and wondering why his other self loved pirate paintings so much.

When the door opened, All for One's patience snapped. He made a break for it.

Yoichi caught him by his collar and dangled him in the air. Smirking, Yoichi said, "You're too slow, squirt."

All for One hissed, "Listen, I'm not your brother."

Yoichi laughed. "I've heard this one before! What are you today? A thief here to steal Dad's staff? A fae changeling? A shapeshifting fox?"

All for One thrashed futilely. "I'm serious! Don't you want your real brother back?"

Yoichi tapped his chin as if considering. "I dunno, I'd be happy to trade you in for a fairy."

"You're still insufferable!" All for One tried to kick his brother. His short legs wouldn't connect. Instead, Yoichi dropped him on his bed and then tickled his ribs until he was breathless from laughter.

All for One moaned, humiliated beyond measure that his stupid little brother had become stronger than him. Maybe if he closed his eyes, this would all turn out to be a dream. He squeezed them shut tightly and tried to block out the world.

All Might's voice said, "He looks like he's in pain."

All Might?! Then could he have returned to his own world? It was all a dream for real? All for One's eyes shot open.

To his horror, he saw a teenage All Might standing in the doorway. Determined to cling to his delusion for as long as possible, All for One said, "I see you were deaged too."

"Are you pretending not to recognize people again?" Yoichi sighed. "You're so embarrassing."

"It's fine, I'll play along," All Might said in his painfully earnest way. "I'm Toshinori Yagi, your father's apprentice—"

"You're a hero!" All for One yelped.

Yoichi nodded. "Yes, you always admired Toshinori. He's the only person who pretends to like your stupid stories. That's why I brought him here to cheer you up."

"That's impossible," All for One said in a deceptively calm voice. "I would never, ever, admire All Might! Even some idiot alternate version of me who became a younger brother would know better! He has hair tufts!"

"Who is All Might?" Toshinori asked, scratching the aforementioned hair tufts. "If you explain to me then I'll play along."

"AHHHHHHHHHHHHHHHHHHHHHHHHHH!" All for One screamed.

Yoichi turned to Toshinori. "Sorry, he's too grumpy to play today. Even with his favorite person."

Toshinori said, "I know who will cheer him up. His second and third favorite people!"

Yoichi's face lit up in a smile. "What a great idea. I'll fire up the teleportation portal."

They left (unfortunately the door locked automatically) and returned a few minutes later. With a flourish, Yoichi waved his arms. "These are my two best friends in the whole world, but I'll graciously share them with you so that we can play together—"

All for One gaped in horror at the spiky heads of Second and Third. "AHHHHHHHHHHHHHHHHHHHHHHHHHH!"

"What's with that reaction?" Second asked. "We brought your favorite snacks!" He held up a bag of gummies.

Third asked Yoichi, "Is he pretending that we're bad guys again?"

Yoichi shook his head. "No, I think my little brother is pretending he's a villain so you're the heroes. Maybe this is his noise attack."

"It's working," Second said, his hands over his ears.

"AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH—"

After screaming long enough, All for One eventually passed out. When he woke up, he was nestled in Izuku's arms. It startled him, seeing that familiar face bigger and older. He'd still been hoping this might turn out to be a dream.

Stroking All for One's hair, Izuku asked, "What's wrong? You're always happy when your brother's friends deign to play with you. You used to be so proud of playing pretend with the big boys."

"Those aren't my friends!" All for One shouted. "They're brother thieves."

Izuku nodded. "Oh, I see, you're jealous of Yoichi's friends for stealing his attention. Don't worry. Your brother likes to tease you, but he still loves you the most."

"No, he doesn't!" All for One shouted, his temper stretched to a breaking point. "He betrayed me and ran off with my quirk, then died!"

"Don't kill off your brother, silly. Yoichi was worried sick when you vanished." Izuku kissed his forehead. "We all love you very much."

An odd pang flashed through All for One. A part of him wanted to hear those words…but they weren't for him. "This isn't my life! I never got a loving family! I grew up living on the streets and eating trash."

Izuku tilted his head. "I know you hate to eat your peas, but we never fed you trash."

"Rats tried to eat me minutes after I was born!"

"Rats?" Izuku frowned. "What an odd lie. Though…you don't look like you're lying…you aren't making your happy lying face…"

Just when All for One started to hope he might have gotten through to his son turned father, a hooting sound came from the window. Izuku set All for One down on the bed, then went to let the owl inside. He opened the letter, his lips moving and mumbles escaping as he read: "Beloved, you found Hisashi? He was playing pirate? But that's quite impossible, Hisashi is here in his bedroom."

The door opened. A second Hisashi wearing a black cape ran in. "Dad! I had such a cool adventure." He hugged his father. "I became King of the Pirates. I order you to no longer serve peas at dinner."

Izuku gaped down in shock. "You…you're definitely my son! But if you're here…then…" His gaze snapped to the bed.

Standing up, All for One crossed his arms. "As I've been telling you, I'm not your son. Can I go back to my world now?"

Izuku stared for a long moment. Then his confusion softened into a smile. "I guess I have three sons now."

All for One sputtered. "What? But…you have to send me back! I have to kill—I mean, uh, I've got my own family."

"No, you don't," Izuku said firmly. "I've always been good at telling when you were truly sincere. What you said back there was true. You have no family and live on the streets. I can't let that happen to any version of my son. I'll look after you and love you from now on."

Feeling faint, All for One swayed. Now of all times Izuku decided to believe him?

Hisashi ran over and measured their heights with his hand. He smirked. "I'm two inches taller! I'm the older brother. I've always wanted to be older than someone."

All for One wailed, "NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!"

OMAKE TIME!

Magician Izuku: That brute in armor might have hurt my son. What kind of bully attacks a child?

Izuku: Cease this All Might slander before we throw you out of the Izukus Union!

#

All for One: You couldn't tell the difference between me and a real child?

Magician Izuku: In all fairness, you have the maturity of a five-year-old.

#

All for One: I can't understand why my little brother won't hug me.

Yoichi: I'm the older brother now.

All for One: Then I certainly won't hug you! Put me down! I demand a return, I wanted an adorable baby brother and I got an older one instead.

#

Izuku: I always wanted Yoichi to have siblings because I got along great with my little brother.

Tenko: And I'm happy to be an uncle.

All for One: Ha-ha, Tomura, you lost the big brother title too!

Tenko: Who's Tomura? Oh, is this another game?

All for One: You were my successor.

Tenko: (Jokingly) Then I'll betray you and steal your title.

All for One: You already know your lines.

#

All for One: I hate you two.

Second: We know you love us.

Third: Yeah, you've always been a little tsundere.

All for One: I'll tsun my hands around your neck!

#

Izuku: Where did you end up?

Hisashi: I became King of the Pirates!

Izuku: I really doubt it.

Hisashi: Yeah, the kid with the straw hat and stretchy arms didn't agree with me either.

#

Izuku: What should we call you two? Big Hisashi and little Hisashi?

All for One: I will not be little Hisashi. In my universe that was merely a fake name. My real name, the name I gave myself because I had no parents, is…All for One!

Izuku: No matter the universe, you're still a chuunibyou. What was that name you said before? Tomura? Do you want to be Tomura?

All for One: NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!

#

Izuku: Why are you so eager to get back to your world? You weren't doing so well when I found you.

All for One: I was about to rule the world!

Izuku: You were about to rewind into a baby and then get beaten.

All for One: It might have seemed that way, but you didn't know my master plan.

Izuku: I bet you would have forgotten your own master plan to throw a temper-tantrum, just like my Hisashi.

All for One: …

Izuku: My son is a kindergartner, what's your excuse?

#

Hisashi: I love my big brother.

All for One: I refuse to acknowledge this Yoichi exists.

Hisashi: Then I win favorite brother by default.

All for One: Listen, you little shit!

Yoichi: It's flattering when they fight over me, but this is the second time they set fire to the tower this week.

#

Shouto: I'm definitely Izuku's husband, right? The author loves me the most!

Ochaco: Excuse me, if we have biological children, then I'm the more logical pick!

Shouto: This is a magical universe, there are other methods of reproduction.

Author: Although I love you two more, I have to admit, when I think about who would make sense as All for One's father both ability and personality wise, I can only imagine Neito Monoma.

Monoma: Absolutely not! Stay away from me, you crazy author!