Chapter 3 (Special thanks to Jokermask18 for the idea. Ending inspired by TMNT episode, "Back to the Egg".)
Big Hero 6 had just managed to finish a fight against a tough opponent and were on their way to grab something to eat.
"Man, nothing like fighting crooks to get you hungry." Wasabi said.
"Indeed. After a great battle, the heroes always go for their well-deserved rewards." Fred said.
Little did they know, someone was watching them and walked into the cafe after them.
As the heroes were waiting for their grub, the person took the seat closest to them, and once they had left the table to take care of business before they ate, slipped something into a small ray gun. Once they came back and ate, they took aim at Hiro as they stepped outside and fired, zapping him with a green ray. Hiro was then covered by a cloud of green smoke.
"Hiro!" Honey Lemon said. Wasabi and Fred looked and saw the perpetrators' shadows as they ran off.
"You thinking who I'm thinking?" Fred asked.
Wasabi nodded before they looked back at Hiro. What they saw shocked them. Hiro and his clothes had been shrunk. He now appeared to be 5 years old.
"Hiro?!" they asked.
Hiro looked at them.
"What was with that funny green light? It kinda tickled." he said.
The rest of them looked at him in shock.
"Okay, WHAT has happened?!" GoGo asked.
"Scanning. Hiro's age appears to have been reduced by 9 years." Baymax said.
"Now he really is Honey Lemon and GoGo's little brother." Fred said, earning a glare from them.
"This isn't funny. Hiro can't stay like this." GoGo said as Honey Lemon picked him up.
"Well, we got a look at the perpetrators as they ran off. Judging by their shadows, I think I know who it was. Me and Fred'll track them down. You guys okay with looking after Hiro?" Wasabi asked.
"Of course." Honey Lemon said as they hurried off with Baymax to find the culprits.
"So, what do we do first?" GoGo asked as Hiro was held by Honey Lemon.
"Umm…Got it! Hiro, do you want to go to the playground?" Honey Lemon asked.
"Yeah! Yeah!" Hiro said.
"Okay." Honey Lemon said. Within a few minutes, they had arrived at the playground and Honey Lemon was pushing Hiro on a swing.
"Higher!" Hiro yelled as Honey Lemon pushed harder and he flew higher.
"Well, this is pretty easy so far." GoGo said as she walked over with some candy for him.
"Yeah." Honey Lemon said before she stopped pushing Hiro and GoGo gave him the candy.
"I wonder what luck Fred and Wasabi are having." GoGo said as Honey Lemon led Hiro back to her car.
Elsewhere, Fred, Wasabi, and Baymax were flying above the city, scanning for any traces of the ray that Hiro was struck with.
"Man, we've searched almost the whole city and nothing." Fred said.
Wasabi then said, "Baymax, anything yet?"
"Scanning. Energy source detected." Baymax said before he flew towards the abandoned warehouses.
"Energy trace is here." Baymax said as he landed on the roof. Fred and Wasabi could make out shadows through the windows.
"Baymax, eavesdrop." Fred said.
Baymax activated his auditory sensors and they heard, "So, he wasn't turned into a baby completely?"
"No, sir." said another voice.
"I want him captured and brought here. Zero will pay for making a mockery out of me." said the first voice.
"Zero?" Fred asked before he and Wasabi realized who it was.
Meanwhile, Hiro was back at Honey Lemon and GoGo's apartment, playing a game with GoGo.
"Come on, Hiro. Almost to the end." GoGo said as he moved his piece close to the end of Candy Land. He pulled a card and made his last move, winning the game.
"Yay!" Honey Lemon said.
"Way to go!" GoGo said as she picked Hiro up.
Suddenly, Honey Lemon's communicator rang.
"Hello?" she answered.
"Honey Lemon, Yama is after Hiro! He's the one who shot that weapon! He's sending out goons to search for him!" Fred said.
Honey Lemon got alarmed before she quickly looked out her window and saw one of Yama's goons headed down the street.
"GoGo, take Hiro and hide!" Honey Lemon said as she fetched her suit. GoGo, realizing there was danger, took Hiro and ran into another room.
Outside, Honey Lemon stepped up to face the goons.
"Take this!" she yelled as she fired several chemballs at them, trapping many of them, but missing several others. She soon found herself using her chempurse like a battering ram for any that got close.
GoGo saw the situation and rushed to help after hiding Hiro.
"Where are those two?!" GoGo asked.
Back at the warehouse, Fred, Wasabi, and Baymax had managed to defeat a majority of the goons, but had failed to stop Yama from getting away.
"We gotta go help them." Fred said.
"Yeah, but we also need to find a way to change Hiro back." Wasabi said before he spotted a particular piece of paper.
Meanwhile, GoGo and Honey Lemon had managed to defeat several thugs, but were left exhausted.
"Is that the last of them?" GoGo asked before they were both grabbed around the throats and held in the air by Yama.
"There is nothing I dislike more than party crashers." Yama said as Honey Lemon and GoGo tried to get free of his grip, but couldn't.
Suddenly, they heard footsteps and a yell of, "Leave my sisters alone, you big bully!"
Hiro then rushed at Yama with a pipe in his hand, which he used to whack Yama in the knee with, making him drop Honey Lemon and GoGo before hopping around holding his knee.
"Hiro!" Honey Lemon said as Yama focused a glare on Hiro before rushing at him with his fist raised, only for Baymax's rocket fist to fly into his face, knocking him out cold.
Baymax then landed with Fred and Wasabi, "Hello." Baymax said.
"Where have you three been?" GoGo asked.
"Sorry it took so long." Wasabi said.
"But, we found something." Fred said before he handed Honey Lemon a piece of paper that had a chemical formula on it.
"This is?" Honey Lemon asked.
"It's the formula for an antidote. Yama must have had it in case something went wrong." Fred said.
Honey Lemon smiled, "I think I can have this whipped up easy." she said.
30 minutes later, Honey Lemon walked up to Hiro and gave him a glass of green liquid.
"Here you go, Hiro." Honey Lemon said.
"I don't want this. It looks gross." Hiro said, pushing the glass back at her.
"Come on, Hiro. I promise it doesn't taste gross." Honey Lemon said.
Hiro looked at the glass with uncertainty before GoGo said, "Drink it and you get ice cream."
At that, Hiro looked excited before he drank the liquid. He started to shake before he was enveloped by a cloud of green smoke. When it cleared, Hiro was back to the way he was before.
"It worked!" Honey Lemon said.
Hiro smiled before he said, "Thanks a lot, guys."