The biggest problem comes from bigger people
"Are you SERIOUSLY making another chemical?!" Sans face-palmed as Frisk was scolding the older skeleton.
"OF COURSE I AM! IT'S FOR SCIENCE!!" Frisk and Sans looked at each-other and nodded.
"Gaster, give us the chemical." The older skeleton frowned. Frisk and Sans both reached up for the chemical. Suddenly the door was bust open by Undyne, carrying Alphys.
"HEY PEOPLE--" But Gaster dropped the chemical on the two kids.
"Oh you gotta be shitting me..." Frisk said face-palming. Suddenly they both GREW instead of shrinking. Frisk frowned at herself. Both of them were now adults. And their clothes grew with them. Gaster pushed his glasses up.
"Huh...so I DID mess up something..." He said humming. Frisk and Sans looked at each other then at themselves.
"WHAT. THE. FUCK GASTER?!" Frisk asked. She crossed her arms under her chest. Sans had to look away. Alphys pushed her glasses up.
"I-I can't b-believe t-this...F-Frisk h-has so much curve--" A sharp bone sent the monsters yelping.
"You say ANYTHING about her curves...i will personally cut all of you into pieces...SANS? YOU ESPECIALLY!" Sans snorted.
"let's be honest old man...this time you really fucked up...but...you know what...? alph's right. she does have curves." Frisk covered her chest frowning as Gaster started chasing his son with a bone.
"GET BACK HERE YOU COWARD!! I JUST WANT TO PEACEFULLY BREAK YOUR LEGS!" Gaster yelled.
"NEVER!!" Sans yelled. This will be a long day.
"I fucking hate this..." Frisk said, shifting uncomfortably as she put on her biggest shirt but it was too tight for her chest. Sans looked up from his phone and smirked.
"i don't..." Frisk smacked him over the head.
"Pervert." She said. Gaster teleported in the room with a bone.
"Sannnnssss...?" He gulped. Frisk chuckled.
"You better run, lover boy. He's got quite the bone to pick with you." He immediately teleported out of the room.
"This sucksss....I so am not in the mood for this..." Frisk says as they were walking towards the store. They needed some stuff so Gaster could actually cook dinner tonight, which meant...Food shopping. Frisk was wearing Sans hoodie since it was the only thing able to hide...ummm...THAT. Sans would however keep glancing in her direction. She would glare at him but she wouldn't complain that much. This was a huge mess caused by the lovely doctor Gaster. Sans sighed as they entered the store. First thing that happened...? A guy whisteled as Frisk walked past. She jumped up and pulled the hoodie better down. It took all his good will not to strangle the fucker right then an there.
The next incident was when they were at the candy asile. Some dumbass grabbed her ass. Frisk turned around and backed away in horror. Sans frowned. He grabbed Frisk and the things they wanted and left. The third however was enough to send him in rage. They were shopping for soap when:
"Hey there mama. You don't need that soap, i can clean you up real good." Oh that's it you sick pervert--
"hey bud? watch your filthy mouth or i may have to shove the soap you're buying in." Sans said with a growl. The guy rolled his eyes at him.
"And what is a little holloween decoration going to do to me huh? Listen, just mind your business man." Sans chuckled.
"what did you call me?" Frisk was balling her fists and gritting her teeth. Oh the guy fucked up.
"A halloween decoration." Frisk came forward. She looked at Sans. He smirked.
"he's all yours baby-bones." The man raised and eye-brow as Frisk nodded and started winding her shoulder. She punched the guy then riased her leg that hit him in his back, that leaving him groaning on the floor. Sans laughed.
"it's not me you should be scared of big guy...it's the 'mama' you were talking about...and i believe you just got dunked on. let's go." Sans said. Frisk smiled as they started walking.
Now that they were older he could do A LOT more stuff. Like? Like having Frisk in his lap no problem. Gaster walked in and immediately froze. Frisk was scrolling through MonsterGram on her phone and Sans was sending another troll message to Papyrus on his fake account.
"OH NO YOU DON'T-- YOUNG LADY GET OFF FROM HIS LAP THIS INSTANT!!" Frisk dropped her phone and had to bend down and pick it up. Gaster saw the way Sans glanced from his phone and smirked. He came closer and hit the skeleton behind his head.
"ow- the hell?!" He said as he rubbed the back of his skull.
"GET YOUR HEAD OUT OF THE GUTTER AND YOUR DIRTY THOUGHTS AWAY FROM MY BABY!!" Gaster yelled. Frisk snorted. She chuckled.
"Don't worry...he saw nothing yet. lol." Sans spurted as he blushed deep blue and Frisk walked up the stairs fast to avoid the father's wrath.
"OH NO YOU DON'T-- FRISK! GET BACK HERE YOU LITTLE-" Sans was looking in one spot with blank sockets. Holy Jesus he won't make it long in this body.
"I hate this so badly!!" Frisk said frowning as she realized her pj's looked like they were a crop top. She sighed. Sans looked her up and down and shrugged.
"i think it suits you...heh." Frisk frowned.
"Don't make me make you sleep on the floor..." Sans snorted.
"what am i? a dog..?" She sat down on his lap and kissed him. He chuckled. Suddenly a very proeminent and over-protective cough could be heard. Frisk pushed away and did a roll on the bed as she got away. Sans froze. Welp shit--
"Who's not a dog? Because i'm pretty sure if you're keeping this up i will make you sleep in the dog house. Frisk, you're sleeping with me. NOW!" Frisk got her pillow quickly and looked at Sans. He shrugged not knowing what to do. Well this level of overprotectiveness was new.
Frisk looked really tired the next morning. And Sans was pretty sure she was tired thank to her eye-bags.
"the hell happened to you?" Sans asked amused.
"That man held a whole damn interogation on my ass then proceeded to lecture me the whole night for doing something that could 'ruin my life so young'." Sans face-palmed.
"you just gave me a kiss...sheesh.." Frisk kissed him again.
"And i just ruined my life twice." Frisk said with a wink. Sans chuckled. She tasted like coffee and pancakes. Gaster coughed. Frisk slammed her mug on the table.
"PLEASE JUST MAKE THIS THING WEAR OFF ALREADY!!" Frisk said. Sans chuckled.
"i don't mind it...i mean...what cup size even is that..?" Gaster smacked Sans again. Frisk looked down confused.
"Now that you mentioned it...I'm curious as well..." Gaster was enraged.
"GET OUT BOTH OF YOU! AND SANS IF YOU DARE LAY A HAND ON HER I SWEAR TO GOD!!" They both got out giggling. Frisk looked at her chest again and got a tape measure. She wrapped it around in multiple places and spurted as she made the calculations.
"what..?" Frisk looked down and frowned.
"This can't be right...I'm a G...?" Frisk asked tilting her head. Sans smirked.
"alright--OW WHERE THE HELL DID THAT EVEN COME FROM!?!" Gaster popped from the kitchen. He picked up his spatula using magic.
"TOUCH HER AND I WILL STRANGLE YOU!!" Sans scoffed.
"no fun..." Gaster face-palmed.
"I raised a pervert..." Frisk started laughing. Sans blushed deep blue.
"DAD WHAT THE HELL--"
Finally the day ended and they were both small again. Frisk jumped up and down in excitement and Sans looked a bit bumed out. Gaster was hugging Frisk tightly.
"OH THANK GOD MY BABY GIRL IS BACK!! DON'T YOU DARE GROW UP!!" Gaster said. Frisk gagged as he tightened his grip.
"I- can't- breathhh!! Gasterrrr!!" Frisk said wiggling her legs. Gaster sniffled and wiped a non-existent tear.
"Ah i am so happy you are back to normal." Sans stared at his father in disbelief.
"I AM RIGHT HERE! AND I AM YOUR SON...BY BLOOD!!" He said. gaster waved his hand dismissing him.
"Yeah yeah whatever...OH FRISKKKK~ DON'T YOU DARE LET MY NUMBSKULL OF A SON TOUCH YOU AGAIN! JUST LET ME LOCK YOU IN YOUR ROOM!! I CAN PROTECT YOU!!" Sans gestured around franatically, still in disbelief at his father. Frisk was laughing.
"Nah, i kinda want to live my life..." Gaster finally let go and Frisk was walking towards the door. Before she reached the door she stopped.
"Oh yeah and Sans...? We grew up until the age of 20. We're pretty close to that future if you ask me personally." She said with a wink. She started walking away, with her hands behind her head. Sans froze and blushed. That girl will be the death of him. Quite literally as Gaster was eye-ing him and summoned a bone.
"WAIT WAIT WAIT SHE APPROACHED ME- SHIT AHHHHH!!" Sans said running as Gaster was running after him.
"JUST LET ME BREAK YOUR LEGS, COWARD! AT LEAST TAKE THE BLAME FOR HER!!" The two were chasing each other around. And they would have done it for a longggg time if Frisk didn't remind them it was dinner time.