Frisk struggled in Toriel's grasp, trying to get free. When Toriel entered the bathroom, she was met with Flowey.
"Flowey, would you mind leaving?" Toriel asked him.
"LEAVE?! I GET A BAR OF SOAP SHOVED DOWN MY THROAT, AND ALL YOU ASK ME TO DO IS LEAV-," Flowey was cut off when he hiccupped, sending bubbles flying from his mouth. Toriel looked at the flower in shock. He hiccupped again, allowing more bubbles to escape. Frisk reached up and popped one, making her giggle. "Stop laughing!" Flowey shouted.
"Um, maybe you should talk to Alphys," Toriel said, picking the potted plant up. She placed Flowey outside of the bathroom, and closed the door. She started the water and filled the tub. After a short battle, Frisk was in the tub. She struggled as Toriel poured water on her hair to get the glitter out. Soon, Frisk was clean. "There, was that so bad?" Toriel said, draining the colored water. Frisk just blew a raspberry at Toriel with her bright blue tongue. Toriel just sighed and dried Frisk off. After another fight, Frisk was dressed. When Undyne had finished cleaning Frisk's mess, they all gathered for dinner. Flowey kept on coughing up more bubbles, and Frisk didn't resist being fed for the first time. After dinner, they all headed down to Alphys's lab.
"So you're saying that you found a way to change her back to her normal age?" Undyne asked.
"I think so, all we have to do is feed her this," Alphys said, holding up a small bottle of green liquid. She handed the bottle to Toriel who was holding Frisk. Toriel sat down with Frisk, and she tried to feed the liquid to Frisk. Frisk however, resisted, feeling that she wasn't hungry or thirsty, given the fact that she just ate. It took a while, but Toriel managed to get Frisk to drink some of it. That was when Frisk sneezed, spraying green liquid everywhere.
"Ugh gross!" Undyne said, wiping the slime off her face. Toriel sighed, setting the bottle down and wiping her face.
"Alphys? Are there any side effects to that stuff that we should worry about?" Sans asked, wiping his arms. Alphys thought for a moment.
"Maybe, considering we all came in contact with it, I'll have to do some calculations," Alphys replied, starting to calculate the situation.
"Well I for one don't like the idea of any side effects," Papyrus said. Toriel sighed.
"We'll try the potion again in the morning," she said, taking Frisk to bed. The other went to bed while Alphys kept on working.
When morning finally arrived, the others were all awoken by Alphys.
"What's with the wakeup call?" Undyne said, still half asleep. When she heard her voice, she gasped and covered her mouth. "What's wrong with my voice?!" She asked, in a higher pitched voice.
"That's what I came to tell you guys! I figured out the side effects to that potion," Alphys said, panicked.
"That potion is basically made to progress age. But considering Frisk's saliva was mixed with what she sprayed last night, it somehow reversed the effects!" Alphys said, still panicked. "When I woke up this morning, I almost fainted in front of the mirror!" She continued.
"I have to see for myself!" Undyne said, running to the bathroom mirror. Seconds later a loud scream was heard from the bathroom. The others ran upstairs to see, but the all stopped in their tracks when they looked in the mirror. Five shocked monster children stared back at them.
"W-We look l-like five year olds!" Toriel said, still staring at her shocked reflection.
"Ugh! I hated being a five year old!" Undyne shouted stomping her foot.
"Undyne! Don't stomp! You might wake up Frisk!" Toriel said, still having some mothering sense to her.
"Fine!" Undyne shouted, folding her arms and pouting.
"Is this going to wear off Alphys?" Toriel asked. Alphys sighed.
"I don't think so, the only way to cure it is to get the antidote," she replied.