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Aizawa was having a normal day, just sitting in his office and grading papers. Then Midoriya came in snickering and giggling behind his hands.
He sighed.
"What is it, problem child?"
"I- pfft- got hit by ahaha- ahaha- a qui- pfftahahaha!" Midoriya struggled to explain his situation and fell into a small laughing fit.
Aizawa put the pieces together. "You got hit by a quirk?"
He nodded and took a few deep breaths, though an occasional giggle kept slipping out.
"How did this happen?"
"A strahange man was harassing a girl and Ihi stepped in. Trihihied to cheheck ohon her and thehen this- ehehe- strahahange pihihink gas. Shehe sahahaid the quirk... pfftahahah- was lahahahaughing gahahas!" Midoriya cracked up like it was a hilarious story.
"Laughing gas, huh?" Aizawa rubbed his temples. "Any idea how long this will last?"
Aizawa waited a moment as Midoriya tried, and failed, to regain composure. He eventually held out 4 fingers.
"Four... hours?"
Midoriya nodded and snorted, which seemed to amuse him into laughing harder.
The teacher sighed. Of course Midoriya of all students would get himself in this situation. At least it wasn't harmful.
"Can you make it to the dorms or do you need help?"
Midoriya stood up, his face pink. His face was contorted into a wobbly grin. "I-I'll behe fihine." He said as he made a swift exit.
Deku continued his deep breathing as he made the trek to the dorms. Every time he'd feel he had calmed down he'd think the same thing. "Don't think of something funny. Don't think of something funny."
Then of course his mind would pull some funny video he watched or Todoroki calling himself 'The Hand Crusher", and he'd be giggling again.
He whined to himself through his mirth thinking about walking through the common room like this.
Eventually this fear came to pass and he stepped up to the main entrance of the dorms. This was going to be extremely embarrassing if he couldn't keep it together.
He took an absurdly long time just trying to calm down, though eventually he took a few good deep breaths and entered.
"Are you alright, Bakugou?"
"What do you mean by that!?"
"You took a substantial hit during training."
"Yeah, and? What the Hell are you looking at, Icyhot?"
"You, currently."
"Hah?"
Bakugou and Todoroki were arguing. Well, it was more like Bakugou arguing with a brick wall with a deadpan expression.
Midoriya couldn't help it if he wanted to. He burst into laughter at the sight, everything seeming 100x funnier than normal, as he doubled over and clutched his stomach.
The entire common area of students turned with bewilderment to the sight at the door.
After a few seconds of silence Bakugou shouted "What the Hell, Deku! Are you laughing at me?" He stomped over to Midoriya who was supporting himself against the doorframe.
The giggly student frantically shook his head.
"Then why the fuck are you laughing like a moron, huh?" Bakugou shouted, sounding more like a demand for an answer than a question.
"Q... Quihihihirk hahahaha! L-Lahahahaughing gahahahas!"
"What? The fuck are you talking about?" Bakugou shouted, rage mixing with genuine confusion.
"Oh! Is he trying to say he got hit by someone's quirk?" Uraraka suggested, smiling about as wide as Midoriya and walking closer to the scene, but not so close that she'd be in explosion range.
"Did you seriously get nailed by some kind of laughing quirk, you idiot?"
"I think he said laughing gas." Uraraka added.
Midoriya quickly nodded as his laughter calmed to occasional giggling.
"Lohohong story. Lahahaughing gas quirk. Fohohour hours."
"That's hilarious! Four hours?" Sero laughed from the kitchen.
Bakugou turned to see half the class stifling laughter of their own.
"Oh Hell, don't tell me the quirk's contagious?!" Bakugou roared, about to get the Hell out of dodge.
"Nah, man." Kirishima giggled a bit before calming himself. "Midoriya's laugh is contagious!"
"Indeed it is." Yaoyorozu added, also fighting back snickers.
"You're all weak as Hell." Bakugou stomped off, bearing a much too intentional and wobbly scowl.
With Bakugou gone, and most of the tension gone with him, Midoriya and a few other students began giggling like their life depended on it.
Another three or so hours of this huh?
He figured he could live with that. A little laughter never hurt anyone. Embarrassed them, maybe, but didn't hurt.
...
As Class 1A unboarded the buses, Midoriya could barely sit still. For some special training, UA classes were going against Ketsubutsu Academy students in a team-on-team battle. He'd brought every notebook he could pack in his small bag for note-taking and was ready to use them.
"There's my future husband!" Ms. Joke yelled as she approached.
Aizawa sighed as if the end of the world was walking his way. "Will one of you talk to her so I can get a break?" He asked his class, probably rhetorically.
Midoriya practically bolted up to her and grabbed one of his notebooks.
"Ms. Joke, the smile hero! I have so many questions about your quirk, i-if you're not too busy!"
The female hero blinked in surprise but quickly returned his smile. "I remember you. Sure, ask away."
"What is the approximate range of your ability? Does its effects have variance from person to person? Like, are certain people easier to make laugh than others? Can you just pinpoint one within a group to activate your quirk or is an area of effect?"
"Whoa, slow down there, kiddo. You sure are excitable aren't you?" She ruffled his hair and the boy smiled wide. "To answer, my quirk is more effective on people who already laugh pretty often. It takes more energy for the grumps like your teacher, you know?"
"That makes sense!" He quickly scribbled something in the margins of his book.
"And, well, why don't I just show you?"
"Joke. Don't." Aizawa warned.
"Show me?" Midoriya cocked his head to the side.
"Like this!" She said and instantly Midoriya was overcome with a massive wave of uncontainable mirth.
The greenette fell to the his hands and knees absolutely laughing his heart out as hard as he had ever thought possible.
Ms. Joke erupted in laughter herself. "Yeah, I can tell you're naturally a giggly person."
"Midoriya?" Todoroki asked, slightly worried. He approached the shaking green student who already seemed out of breath from his own cackling.
"Enough." Aizawa's eyes went red and Midoriya was released. He quickly took in breaths as fast as he could.
"Are you alright, Deku?" Uraraka asked.
"That was amazing!" Midoriya picked himself off the ground with zero hesitance. "Not only does it cause laughter, but euphoria as well. It's different from the laughter from, say, being tickled, because it does cause joy as well as a laughter response!" He rambled and went back to jotting down notes.
Mr. Joke cackled and slapped her knee. "This kid's a riot. Can I keep him?"
"No." Came Aizawa's deadpanned response, causing Ms. Joke to laugh again.
...
"I'm happy to see you've turned your life around." Midoriya said to his phone.
"As am I, Deku. This artist makes people laugh for villainy no more!"
"I'm glad to hear that, Smiley."
After Mr. Smiley had gotten out of jail (with his offenses being minor, it was a short stay), he had taken to facetiming Deku regularly. He carried great fondness for the hero who showed him the light, and Midoriya enjoyed their chats. His art was getting better and Smiley was just a fun person to talk to.
"Who ya talkin' to, Mido?" Kiri asked as he walked into the common area. Midoriya was sitting on the couch, with Mr. Smiley having called while he was eating dinner.
Bakugou came in after. "Stop talking out in the open, nerd."
"My apologies for calling you at this time." The artist said.
"Wait a minute. That voice- is that the smile bastard?" Bakugou shouted.
"The very same!" Mr. Smiley announced and flashed a grin.
Oh no.
Midoriya had a half a second to realize the faint rainbow aura before he exploded into hysterical laughter.
"Oops, sorry! Reflex!" Came the voice from the phone which had been dropped to the floor.
Midoriya was collapsed on the couch cackling his little heart out.
"This is why you don't facetime with villains, you idiot!" Bakugou yelled.
"Oh, damn. That lasts hours, right? Should we bring him back to his room?" Kirishima asked, staring blankly at the pile of green mirth before him.
"Apologies! I best hang up now. Give him my condolences in two hours!" With that, the artist hung up.
Bakugou grit his teeth. That was one of the dumbest things Deku had ever done. He couldn't care less if the nerd wanted to chat with a weakass retired villain over a phone call, but over facetime where the guy's quirk can affect him? That was stupid.
"How the Hell do you keep getting yourself into these situations, huh?" Bakugou nudged Midoriya in the ribs with his foot.
"You say that like you didn't get hit by Smiley's quirk three times." Kirishima said with a grin.
"We were fighting the bastard, this idiot just invited his quirk over for a damn tea party."
Kirishima snorted and began giggling. Bakugou's gaze tightened. "What's your problem?"
"Sorry. He's just got a really infectious laugh."
Bakugou rolled his eyes, pretending he wasn't having trouble keeping the frown on his face.
"What's Deku laughing at?" Uraraka exited the elevator to the commons with Yaomomo in tow. They both smiled, albeit a bit confusedly, at the sigh and sound of Midoriya, once again, losing his mind laughing.
"Moron Facetimed the guy with the smile quirk."
"Wait, the artist who you guys fought? The one on tv that made us all laugh?" Uraraka cocked her head in confusion.
"Yeah. Even for Midoriya, that's kind of a reckless move." Kirishima said, starting to agree with Bakugou. Something was a bit weird about this.
Uraraka and Momo were stifling snickers, still affected by Midoriya's adorable laughter.
"I'll take him to his room. It's gonna be a couple hours, right?" Uraraka took Midoriya into her arms while he continued cackling like a madman, completely oblivious to his surroundings.
"Yep. Sucks for him." Bakugou left for the kitchen for some food. Though, as he went, he couldn't help but think. Deku was smarter than that. If he wanted to keep in touch with the smile idiot, he could've just phonecalled. Why Facetime?
He'd gotten hit by a couple laughing quirks lately. That can't be coincidence.
Bakugou pulled out his phone. He, unfortunately, was a part of the big 1-A groupchat. He didn't really contribute much but would scan through the texts occasionally to see if there was anything he should be aware of. He remembered back to that laughing gas quirk. Some extras had asked about the incident and Deku explained it in the chat.
He scrolled back and read through the texts.
There.
According to Deku, a man was harassing a young girl. The girl shoved the man away and let out some of the pink laughing gas, sending the man into a fit. Deku claimed that he approached the girl to ensure no injuries, but was caught in the gas.
Deku wasn't normally THAT careless. The only thing that made sense was that Deku saw what the gas did, and intentionally exposed himself to it.
And just the other day, when they went to Ketsubutsu Academy. Midoriya seemed much too eager to grill Mrs. Joke about her quirk. Well, that wasn't weird in and of itself, but he didn't seem to be too wary when Mrs. Joke offered to demonstrate her quirk, clearly implying him to be the target. At the time, he chalked it up to him being an idiot, but now, he had drawn another conclusion.
Deku seemed pretty fucking desperate to laugh his ass off for some reason.
And Bakugou was gonna get the nerd to spill why.
...
Deku panted and coughed as he finally got a hold of himself. The quirk had worn off, but he still wore a grin bright as the sun. That was exactly what he needed.
It was great, but still took a lot out of him. You'd be surprised just how exhausting and physically demanding it is to laugh uncontrollably for two hours.
He vaguely remembered someone bringing him up here, which was... embarrassing. He probably shouldn't have been facetiming Mr. Smiley in the commons, but that's where he had called.
He definitely needed to make this a regular thing. He was already looking forward to the next time.
...
It had been a few days since Deku's latest laugh-quirk run-in. Bakugou was the living room Kirishima and Kaminari as they discussed some movie he didn't care about. He eyed Deku across the room. He had no idea why he was so invested in this nerd's weirdness but he was, and he was going to get answers.
"Alright, I'm just gonna head up to my dorm. Gonna facetime, uh- someone."
Bakugou's gaze tightened. Was he really about Facetime that smile bastard again?!
He waited for a moment, not wanting people to think he was following Deku (which was exactly what he was doing), before heading to the elevator.
...
Deku had been so excited when he was heading to his dorm. He was hoping maybe Smiley would flash that grin again, but then the artist texted him that something had come up and they couldn't chat.
He had texted back that was fine, and it was! It was totally fine.
Completely fine.
Deku slumped against his bed and sighed. What to do now?
Someone knocked at his door.
"Come in." He called, expecting Uraraka or maybe Iida.
Instead, Bakugou entered.
"Kacchan? What are you doing here?"
"What's been up with you lately?" Bakugou wasted no time.
"Uh, what do you mean?" Midoriya stammered, suddenly ramrod straight and nervous as ever.
If Bakugou had needed confirmation that something was up, that would've been it.
"Why are you do desperate to laugh all of a sudden?"
"What? W-Why do you say that?" Midoriya averted his gaze and chewed on his lip. He'd always been a terrible liar.
"You purposefully went into that laughing gas quirk, didn't you? And wanted Mrs. Joke to use her quirk on you? Then you go and fucking Facetime the guy that makes people laugh with a live image."
"I-I have no idea what you're talking about. And, uh, I don't mean to sound rude, but, why do you care?"
Bakugou blinked. That was actually a good question. Why did he care?
Images of Deku laughing and smiling flashed through his mind. Memories of that laugh echoed in his head. And with those recent memories, came faded images of 4-year old Deku laughing with him, back when things were simpler.
"Doesn't matter. Now spill."
Midoriya gave a shy smile and sighed. "I guess I'm not a great liar, huh?"
"No. You're pretty shit at it."
"I guess... it started when Mr. Smiley used his quirk on us while we were on patrol. It felt... great."
"You actually enjoyed that?"
"Well, I felt ashamed that we weren't able to catch a villain, but, that was after the quirk wore off. While I was laughing, I could barely think about anything except... how good it felt to laugh." Deku chuckled. "I couldn't even think about the pain of crashing into the wall."
"So what, you just wanna stop thinking?"
"Maybe. It's also just... laughing feels so good. There's so much to think about now. The league, All For One, my quirk, all of it... Sometimes, my smile doesn't feel real, but when I'm laughing that hard, I smile so wide my cheeks hurt!"
Bakugou was quiet, electing to listen to Deku's thoughtful rambling.
"And, well, I laughed a lot more as a kid. Remember, Kacchan? When we'd watch a funny show, or make up stories, or even just get in tickle fights."
Bakugou huffed something akin to a chuckle. "Yeah, you were so ticklish it just took a couple pokes to get you going."
"I miss that." Deku smiled. "I wonder if I'm still ticklish."
Bakugou snickered. "There's no way you're not."
"How do you know that?"
"There's no universe in which you're not a helpless ticklish nerd." Bakugou scoffed. He paused for a second, remembering Deku's face as he laughed. "I'll prove it to you."
"W-Wait, what?" Deku stammered and shuffled back so he was sat up against his headboard.
"You heard me." Bakugou grinned lunged onto his bed. He grabbed Deku's wrists and shoved them onto the headboard just above Deku's head. "You wanna laugh so bad? Stop using dumbass quirks to do it. I can make you laugh a thousand times harder than any useless quirk."
Midoriya grinned wide and bit his lip. "N-Noho! People wihill hear!"
"Well that's just too damn bad for you then, isn't it?" The blonde wasted no more time before digging a full hand of wiggling fingers into Deku's sides, while the other kept his hands above him.
Deku squealed and chomped down on his lip to keep from laughing.
"The Hell? I thought you wanted to laugh your ass off?"
"Th-they'll hehear!" He grunted out. He was squirming from side to side as his mind tried to decide between staying still to take it and fleeing.
"Pfft. You embarrassed people will hear you and know you're stupidly ticklish?"
Deku frantically nodded.
Bakugou leaned in close so his breath tickled the greenette's ear. "You think I give a shit?"
Once Deku felt fingers clawing at his ribs, he had no hope of holding back anymore.
"PFFTAHAHAHA! KAHAHAHACCHAN!"
Bakugou grinned victoriously and sat back, enjoying the sight. The nerd's laugh had never sounded so good.
"What's the matter? Too much for you?" He sneered and switched his tickling to the greenette's sides, hoping to find a sweet spot.
Disappointingly, his laughter died down a bit into giddy giggling.
Bakugou fought it. He really did, but hearing that hysterical giggling and staring at that pink face with a bright smile, it did something to him. As much as he hated it, he found himself huffing out something he'd deny to be giggling to his grave.
"Damn extras are right." Bakugou laughed. "Your dumbass laugh is contagious. You really can't take it, can you? Too ticklish for your own good."
"Ihihi cahahan tahahake it!"
"You think you can, huh? Don't think I can break you? I'll tickle you so bad you'll wish you were never born!"
Bakugou's competitive spirit flared and burned with his need to hear more of that laugh into a raging inferno that Midoriya would never be able to stop, not that he wanted to.
"Kahahahacchan!"
"Did you forget how much I destroyed you back then? I can do it again. Let's see... Oh right, I remember!" Bakugou, once again, grabbed Midoriya's wrists and hoisted them above his head with one. He wiggled his fingers on the other with a grin, absolutely relishing in Midoriya's hysterical giggles just at the threat of tickles.
"This one drove you crazy." He then began jabbing two fingers into his unprotected underarm over and over again.
Midoriya shrieked and began thrashing in hysterical laughter.
"KAHAHAHACCHAHAHAHAN!"
"Heh. Tickle tickle, weak lil' Deku! What was that about being able to take it?"
Midoriya tried clamping down on his lip a few times or holding his breath to just stop laughing, but mortifyingly for him, it only made him snort pretty loudly before bursting right back into uncontrollable laughter. And each snort came with Bakugou laughing at his expense.
"Let's try down here." Bakugou stopped his jabbing and released the nerd's hands in order to rest his hands on Deku's hips. "I remember this spot being so ticklish you'd scream!
Midoriya, without any wiggling or movement of the fingers on his hips, was so ticklish that he bucked, squealed, and and fell into a fit of giggling... just at their mere presence.
"Ohoho... this is gonna be good." Bakugou grinned in the most delightfully sadistic manner. "Any last words, nerd?"
"Pfftahaha- K-Kacchan- nohohot thehehere! Anywhere buhuhuhut thehehehere!"
"Oh I am so gonna tickle your hips until you beg for mercy, shitty Deku." He wasted no more time before scribbling and squeezing all over Deku's deliciously sensitive hipbones.
Poor, poor Midoriya positively screamed in laughter and bucked and thrashed like his very life depended on it. He writhed, fought, pounded his fists on the bed, and laughed harder than he ever had in his life.
His core ached, his cheeks hurt, his face burned, and his chest spasmed at the sheer force of his own cackling.
Bakugou wasn't too far behind him, so immensely amused at the mirthful suffering of his rival that he was laughing hard as he tickled Midoriya to tears.
"God, this is priceless. How fucking ticklish are you, huh? You sound like you're dying." Bakugou laughed. He quickly figured out he couldn't expect a response from Midoriya in this state. The nerd didn't even seem like he could comprehend anything going on around him.
"I think I'll just stay here for a few minutes. Unless you have something to say?" He grinned when Deku didn't give him any acknowledgement, just continued to laugh and laugh and LAUGH.
And laugh he did for the next five minutes of ticklish Hell because Bakugou didn't leave his hips once.
And so when he finally let up, Midoriya immediately went limp and gasped for air as if it was his first time breathing in hours. A permanent dopey grin was plastered to his face and his eyes were half-closed as he rode out the leftover giggle fit.
"How was that for laughter, huh? And you said you could take it. You look half-dead!" Bakugou sneered as he admired his handiwork.
One Deku, utterly broken.
"Th-thahat..." Midoriya coughed. "-wahas amazing."
"The Hell? You still enjoyed that?
Midoriya nodded his head as he finally stopped tittering.
"You're insane."
Aaaand Midoriya fell back into giggling.
And Bakugou couldn't deny... those giggles were contagious.
If Deku wanted to laugh so bad, it was a good thing he was so ticklish, cause Bakugou was planning to abuse that weakness on the regular from now on.