A few months passed, months of care, and shared naptimes. Papyrus thought Sans was starting to be a bad influence, but at the same time, it was often too darn adorable to interrupt. Today Undyne was over with Papyrus chatting with him in the living room as Sans laid in front of Frisk, who playing on her blanket with her favorite toys. Sans was a little ways away and the child tilted her head back to see him. With a little grunt, she managed to roll herself over, catching Undyne and Papyrus' eye.
"Oh hey, what are you up to shrimp?" Undyne said with a smile, as she did so, she saw that Frisk was propping herself up on her arms, with her face brimming with determination. Her legs arched and fell, and she flopped back onto the floor.
"You got this Frisk, keep at it!"
"YOU ALMOST HAD IT! GOOD JOB FRISK!" Frisk slammed her hand down, looking more determined than before. Once more, she propped herself up, and this time, she got her legs to bend under her and into a crawling position. A look of elation spread across her face as she put one hand forward, a knee forward, crap wrong knee. Frisk fell back to the ground, this time, she let out a small wail of frustration.
"C'mon punk you can do it!"
"come on over kiddo, you got this." Sans said as he continued to lay on the floor. Once more Frisk got into her crawling position and started to move forward. With each successful move forward, she started moving faster, giggling wildly as she neared her father.
"That's it! You've almost got him!"
"EXCELLENTLY DONE FRISK, NYEH HEH HEH!" The child crawled to Sans, grinning at his face.
"well hey there, howsit goin?" To which Frisk raised her hands and proceeded to pull herself on top of his ribcage. Sans chuckled lightly before looking over to Papyrus and Undyne.
"welp, looks like i'm not going anywhere any time soon." Sans said as Frisk began to babble, to which Sans' replied until they both fell asleep.
"Alright fine, but only because this is too adorable." Undyne muttered, Later on she was definitely going to tell Alphys all about it. But for now, Papyrus and Undyne went outside and into Waterfall to spar, letting Sans and the kid sleep.
Papyrus made sure to baby proof the entire house. Since Frisk was now able to move almost freely, she could get hurt! Asgore and Undyne helped set up proper precautions, though the effort was mostly lead by Asgore, as he had done all of this once before. However, none of them expected to find that, before they safety-blocked the stairs, Frisk had crawled up it and into Sans' room and found a fun ride. It was when they heard giggling and laughing upstairs that they began to investigate, to find that Frisk had taken a joy ride in Sans' thankfully empty trash tornado. The small child laughed with glee as she spun around, Causing Sans to shake his head.
" havin a fun time kiddo?" Frisk responded with a happy squeal and reached out to Sans.
" alright, let's getcha outta there." Sans said as he plucked his kid from the mini tornado. Frisk was in his arms, spinning her head around and giggling. Sans exited his room and made his way downstairs, making sure to inform Asgore that they need to put something up around the trash tornado as well.
During night time, Sans found himself or Papyrus up for most of it caring for Frisk whenever she started to get hungry. But what surprised Papyrus the most was that often times, by the time he got up, Sans was already there with a bottle in hand. Some of these times, Papyrus would actually insist that Sans get some rest while he takes care of Frisk, if only so that Sans wouldn't potentially force himself to stay up all hours of the night.
Often times Sans would take Frisk with him on trips to Grillby's and let her play with the dogs. Now that she had been crawling for quite a while now greater dog had started getting out of his armor and began to let frisk use him to hold herself up on her feet. Together they both moved slowly around the bar, receiving greetings from the other dogs. He had been spending a little less time going to the old ruins door, but when he did, he usually had quite the tale. The old lady seemed to enjoy it when Sans talked about his kid, just as much, if not more than when he was cracking jokes.
Sans took his daughter to another checkup with Dr. Alphys, the small child smiling and holding her arms out to the familiar yellow monster, Babbling excitedly.
"O-Oh! Y-you want me to hold you?"
" go for it al, she don't bite." Alphys took Frisk into her arms and smiled.
"A-Are you ready for your checkup? " Frisk only responded with a smile, reaching her hand out touching the side of Alphys' face, still babbling in the most adorable fashion.
"Alright then, l-lets begin then shall we?" While Alphys was running the usual tests, she began to speak with Sans.
"S-So I may have figured out something. Once F-Frisk started crawling, that would mean she was anywhere from s-six to ten months, and sh-shes been doing t-that for a little while, almost a full month!. A-and while Frisk C-Could start learning how to walk soon, she may only m-master it at around the 16-17 month mark. B-By my estimate, Frisk has about 4 or so months until their f-first birthday, so it seems that monster and human babies are f-fairly similar in that regard." Sans nodded as Frisk yawned in Alphys' grasp, snuggling into her lab coat. Alphys handed Frisk over to Sans and with a poof, they were back in their home. After a few more months, Sans, Papyrus, Alphys, Undyne, And Asgore gave frisk her first birthday party, and all cheered for many more to come. And of course, they had to replace the table because Undyne suplexed Papyrus through it in her excitement. Nobody was surprised.
As the house emptied of guests, Frisk crawled to her father, holding her hands up to be carried. Sans obliged and Frisk patted Sans' cheekbones.
"Da….da...daddy! Daddy daddy!" Sans' eye lights turned to stars for a moment, and Papyrus had just walked into the room.
"SANS COULD YOU-...BROTHER? ARE YOU ALRIGHT?" Papyrus' voice brought Sans back down to earth, his smile wider than Papyrus had seen in a long time.
"y-yeah bro…...heh, listen to this. whos right here kiddo?" Frisk smiled, patting her father's face
"Daddy!" Papyrus was ecstatic "OH MY GOD! HER FIRST WORD! AMAZING! DO YOU THINK SHE'LL LEARN HOW TO SAY MINE NEXT?!" causing Frisk to look over and hold out her hand to Papyrus.
"Pa….pap….y….Pappy! Pappy!" Frisk said with a smile, earning a shocked gasp from Papyrus.
"OH MY GOD THEY CALLED ME PAPPY! THIS IS THE GREATEST DAY EVER!" and Sans couldn't agree more. Frisk spent most of that day repeating those words.
After a month had passed, Frisk began her solo attempts to walk. These attempts often consisted of her plopping down before she could stand, or her falling onto her butt. Papyrus and Sans offered encouragement as the child became more and more determined to walk. She got up on her feet, and took a step, and then another, and another. She had begun laughing in triumph as she made her way to Sans, only to lose her balance and fall on her butt again. She let out a frustrated wail and slammed her hand on the ground. However, Frisk was not done yet, she got herself up again, and finally managed to walk all the way to Sans with a pleased grin on her face.
"Daddy! Pappy! Didit!" Sans was beaming at his daughter
"you did! nice work kiddo!" and once more, Papyrus had not heard Sans have that kind of energy in his voice for quite some time.
"AMAZING WORK FRISK! NYEH HEH HEH!"
"Nyah hah hah!" Frisk laughed, throwing her arms up into the air.
And if one had listened close enough, one might have sworn Sans uttered a muffled "mweh heh heh."