The girls of class 1-A all sat in the common room. The boys had already left for the school wide Halloween party while the girls were “getting ready”. There was some truth to this statement as the girls had to wait to bring out their costumes. Momo splurged for all the girls and got special Halloween costumes that changed people to fit the costume, though she kept what everyone was becoming a secret… except for the invisible girl in the center of the room. Toru was standing in what looked to be a giant bag, holding a small vial in her hand.
“Okay! So as I said, I’m keeping these a secret until you change except for Toru. I’ve checked and these things don’t make her visible so I found something better. The store I got our costumes from also sold big inflatable like costumes that you grow to fit into!” Momo said with excitement, pointing at the bag around Toru’s feet. “So you just put this tablet in your mouth, seal up the costume and you’re ready for the party!” Momo said, handing the invisible girl said tablet.
Toru slipped the pill in her mouth as she put her arms and legs into the costume, Momo zipping up the costume and sealing her in. Toru swallowed the tablet and immediately felt all bubbly inside. The girls watched the floating bag start to inflate, the human shape within it starting to expand upwards and outwards. They watched the bottom fill it’s blocky outline, getting rid of any wrinkles the costume had once had. The thighs started swelling like balloons, one portion of the thighs growing larger than the portion below it. The stomach swelled outward, a faint imprint of breasts pressed against the costume before it faded into the flat but puffy chest of the character. The girls watched the arms swell up next, the forearms getting as large as the thighs. The fingers in the glove like hand began to swell, the tips flattening out while a fifth finger pressed against the confine of the costume but slowly faded away. The only infilled part of the costume was the mask, which slowly began to fill out as the head inside swelled like the rest of the body. Toru’s change was complete, prompting Momo to put the rest of the costume on her. A red handkerchief with a blue collar, and a puffy white hat with the name “Stay Puft” on it.
“Oh! She’s supposed to be that big marshmallow guy from Ghoulbusters!” Tsuyu said while hopping over to Toru. She put her hand against Toru’s new rotund figure and pressed into it, finding little resistance as if she was now filled with air.
“Stop it Tsuyu! That tickles!” Toru said, waving her big arms. “But this was a great idea Momo! This is so much fun!” Toru said, bouncing around and testing her soft body.
“I’m glad you like it! Now, who’s next? I’ll give you the vial you need and hand you your costume as you need it!” Momo said, pulling out a rack of vials with the girl’s names on it.
“I’ll go, I’m super interested now.” Tsuyu said, hoping over to Momo.
Momo handed her a green vial and a black robe with holes in the back. “I would put the robe on first before drinking that.” She suggested to the frog girl.
Tsuyu took the advice and slipped on the robe. Tsuyu took the next step and drank the liquid in the vial and handed it back to Momo, feeling something begin to course through her body. Tsuyu suddenly shot up, her normally hunched over form straightening out and surprising all the girls in the room. Tsuyu watched her pinkies suddenly shrink away while the rest of her fingers became webbed together, the nails turning black and sharpening into talons. Tsuyu then felt her back start to bulge outwards, poking through two holes in the back of the robe. The two bulges began to take shape and form into large green wings, that began to flap at Tsuyu’s control. Tsuyu’s face began to feel weird as many little tendrils began to grow out and cover her mouth. Her hair began to fall out as the back of her head began to elongate into a large octopus head, turning Tsuyu the frog into Cthulu.
“Wow! She looks so cool!” Uraraka said, running up to Tsuyu. She was immediately met with Tsuyu using her face tentacles to poke at Uraraka’s face.
“I’m down to go next,” Jiro said while turning towards Momo, which brought a smile to Momo’s face.
“Here, you need this.” Momo said, handing the punk rocker an outfit that would definitely not fit her. It was an outfit made of black leather straps and nothing else.
“Momo, I won’t even be able to make it pass Iida with this thing on, especially with Aizawa chaperoning the party.” Jiro said, starting to put on the ill fitting outfit. “Look! Even you can’t fill this thing in!” Jiro said, having to hold up all the pieces of the costume.
“You still need this silly,” Momo said, suddenly pouring Jiro serum into her mouth. “Besides, Iida isn’t here tonight and Aizawa will be dealing with the teachers.” Momo explained as she backed away from Jiro.
Jiro felt a raging fire infect her entire body. Her forehead began to bulge outwards as large black horns began to grow out from her head and spiral into sharp points. Her skin began to turn red as blood, her black hair growing longer and cascading down her back. Jiro’s lips swelled slightly as tiny imperfections in her face faded away. Jiro started growing taller as her body began to fit the outfit that hung off her body. Her modest bust began to swell and swell, eclipsing the other girls' busts and soon even Momo’s. Jiro’s ass received the same treatment, swelling and filling the leather costume that was draped around her body. Jiro’s outfit now fit snugly around her body, a little too snug as it rubbed her body anytime she moved. Jiro arched her back as big leathery wings burst forth along with a spade tipped tail. Jiro let out a laugh, her voice now a little deeper. “Now this… I can get behind!” She said, starting to float around the room. She drew oohs and aahs from the other girls watching.
Momo picked out her serum and costume, drinking it down as the others were transfixed by Jiro. Her spiky black hair began to friz out, as if electricity was running through it. Momo slipped on some wild goggles as she began to subconsciously lean forward while her back began to bulge outward. Momo’s boobs surged in size slightly as she put on a white lab coat and yellow gloves. Momo was now essentially bending over as she developed a large hunch. “Testing… testing… testing! There we are, my lisssp.” Momo shouted, drawing all the girl’s attention to her hunched form. “No group is complete without a mad scientist!” Momo shouted as she wobbled over to the other girls. “Now Mina and Uraraka, let’s go outssside for your cosstumes. They’re much bigger than oursss.” She said wobbling outside.
As all the girls made it outside, Mina was jumping with excitement and ready to change. Momo could see that excitement and let her go first. Mina drank down her serum with vigor as slipped on the black dress that Momo handed her. “Hey Momo, I think part of the costume is missing. My whole backside is hanging out.” She said as she felt the serum start coursing through her body. A large black bump began to grow out of Mina’s back as black chitin covered her arms. The bump kept growing bigger and bigger as eight long legs began to emerge from it. Mina was lifted from the ground by her new lower body as six more eyes popped into existence on her face. “I take it back, now I get it!” Mina said, a smile showing off her new sharp teeth as well.
Momo turned towards Uraraka as the others checked out Mina. “You’re up! Here’ssss the ssserum!” She said, handing Uraraka the serum.
Uraraka took the serum and slowly drank it down. Uraraka didn’t feel any different until she looked at the moon, her eyes transfixed on it as they turned yellow. Uraraka began to growl as she started growing, the little fat on her body turning into muscle as she got taller. Her teeth began to sharpen while her face pushed forward into a large muzzle, her ears moving to the top of her head and growing to a point. Uraraka’s fingers grew slightly longer while her nails turned into sharp claws. Uraraka finally stopped growing when she was just shorter than Mina, her legs toned and covered in fur. Uraraka lifted her head to the sky and let out a loud howl, the girls cheering with her. With that, their halloween night truly began.