By the time Gaster finally reached the door to his house, most of the lights in Snowdin were off, even Grillby's bar was closed for the night when Gaster clumsily reached for his keys in his disheveled lab coat. Normally he doesn't have to work so late and have the boys be alone at such an ungodly hour, but this wasn't the first time, and Sans is old enough to take care of himself and his brother, Papyrus, on his own. No, what made the father worried was how the lights of the house were still on despite everything else being pitch black.

Finally finding the correct key in the jumble of 10+ keys on his keyring, Gaster unlocked the door and stepped inside. He was met with a nice, warm temperature change but it wasn't enough to quell the butterflies in his non-existent stomach. The house was silent, dead silent. Sans and Papyrus weren't on the couch, nor in the kitchen, despite all the lights being on. Gaster was going to call for them when he stopped himself and decided against it. There was a small piece of him that wondered if Sans and Papyrus were already in bed and simply just forgot to turn off all the lights—or maybe even the youngest decided to turn every light on just so he could get that glass of water downstairs without worrying about the scary darkness to and from his room like that one time.

Gaster didn't even bother hanging his lab and outer coat on the rack, he unceremoniously dropped it by the door with his suitcase. He could worry about that in the morning.

He began ticking the lights off, one by one, as he checked each individual room. Kitchen. The closet under the sink. Living room. Nope. No babybones were left lying around.

He made his way upstairs, immediately towards the first room upstairs, Papyrus'. He gently creaked the door open to find the room actually dark. He swiveled his eye lights over to the racecar bed, only for there to be no skeleton underneath the disheveled sheets. Gaster's soul jumped into his throat as he swung the door open and turned the lights on. The room was messy, just like any eight-year-old room would be, but no skeleton.

Gaster took a deep breath. It's not time to panic just yet, Papyrus may be sleeping in Sans' room, or both may be sleeping in his room, so they could be tucked in in their own beds no matter the time Gaster gets home, such was common when he worked extremely late.

He turned off the light and quietly shut the door before making his way to his room next. Just as he was about to open his door, the sound of sobbing made him freeze. Fatherly instincts kicking in, he ignored the harsh beating of his soul in his head and listened to where the sound was coming from, and briskly walked towards the direction of the sound. He ended up in front of Sans' door.

He leaned his head against the door. He could hear the muffled voices of what sounded like his youngest, Papyrus, but not Sans'. Instead, he heard whining and small, cries of pain, whimpering and sobbing. Alarmed, Gaster twisted the knob aggressively only to find it locked.

Red flags flying, he knocked on the door. "Sans? Papyrus?"

There was another set of muffled voices, but this time Sans' voice could be heard amongst Papyrus', but it sounded very frail and weak. Gaster couldn't figure out which was more alarming, that Papyrus has remained quiet, or Sans hasn't taken advantage of his 'knocking' for one of his jokes.

He pounded on the door. "Sans! Papyrus! Open this door right now!"

"H-hang on, dad!" Papyrus squeaked from the other side. "I-I'll unlock it in a sec."

"p-papyrus no!" Sans' voice sounded hoarse. It sounded like he was in pain.

"B-but Sans! You n-need help!"

"What's going on?!" Gaster yelled as he continued to jimmy the doorknob. "Are you hurt Sans? Please let me in right now."

"C-coming!" Papyrus' footsteps could be heard padding closer.

"n-no! no no no!" Sans pleaded in a strained voice.

With a faint click sound, the door was unlocked and Gaster rushed in.

When he entered Sans' room he froze.

There, cradling himself in a fetal position in the corner of his room, was Sans. Sharp intrusions peeked out of Sans' pajamas and there were evident claw marks on his sleeves from where his hands- no, claws were gripping. The room was partially illuminated by Sans' yellow and blue eye, showcasing his new canines and bristles forming on the top of his head. Sans recoiled when he caught his father's gaze and curled himself further into a ball.

"d-don't look at me! don't…don't…" Sans whined.

Gaster's eyes lit up in recognition and glowed warmly for the poor boy. "Oh Sans, no…it's going to be okay."

Papyrus grabbed his father's hand and held him closely. Gaster placed his hand on his youngest boy and knelt down to his level. "Daddy, what's wrong with Sans? Is he sick? I tried helping, I really did! But…but…I don't how to…" Papyrus sniffled, magic beginning to pour from his eyes.

"Don't worry, Papyrus, your brother is going to be okay." Gaster glanced back at Sans, Papyrus mirroring him as they both watched poor Sans sob. He glanced back at Papyrus. "Would you like to help me make Sans feel better?" Papyrus viciously nodded, almost headbutting himself against Gaster's knee, much to the father's dismay. He had to prop his hand on his son's head to make sure he stopped short of his knee. "I need you to go get my room ready, move stuff off the floor, and grab the painkillers from the bathroom and put it on the nightstand. After that, I want you to get the heating blanket from the closet downstairs as well as a glass of water to go with the medicine. Can you do all that?"

Papyrus saluted. "Yes I can!"

Gaster patted Papyrus on the head and the little one immediately ran out of the room. With Papyrus gone, Gaster stood back up and slowly made his way over to Sans. With every step he took, Sans shrunk away until he firmly pressed himself against the wall. His blue and yellow eye still glowed brightly as ever as the sound of tears and bones cracking overcame the silence. Sans wailed as his body continued to change against his will.

The minute a pained shriek escaped Sans Gaster rushed to his side, no longer prioritizing calming the boy down as his transformation continued to get worse.

"Sans. Sans it's going to be okay. You're going to be okay." Gaster carefully wrapped his arms around his son's body, being careful of the intrusions poking out. Sans flinched at his father's touch at first, but the longer he held him the more he began to cling to him instead. Sans' claws gripped his father's shirt and caused a few tears of his own, but Gaster was unfazed by it. He held his boy close to him, putting him into his lap and craning his neck so his head was atop his son's. "You're going to be okay Sans," he whispered, rocking side to side. "Just take a deep breath." He inhaled. "And let it out." Then exhaled.

He repeated the breathing exercise, able to coerce Sans into doing it—although with warbled sniffs and coughs.

Then a loud snap was heard, and Sans screamed. He clenched his claws against Gaster's ribs, and the older man held in his own scream as he could feel the pain escalate under Sans' grip, but he refused to pull away. Instead, he held Sans tighter and continued to coo, whispering how Sans is going to be okay and that this wasn't going to last forever.

When it appeared the pain from the earlier crack ebbed away a little, Sans finally loosen his grip. "d-dad…" He sniffled, burrowing his head further into the crook of Gaster's neck. "it hurts…it hurts…so bad!"

"I know. I know, but it'll pass, I promise." Gaster replied, "The first time is always the hardest."

"f-first t-t-time?" Sans hiccupped.

Then there was another snap, but this one was much louder than before, and it was only the first of many. This time Sans pushed Gaster away and rolled from his lap, his body convulsing as his spine continued to snap and crack as it grew into a tail. Sans' scream turned hoarse and deeper as he gripped his head, feeling his skull elongate into a snout.

Gaster's eyes grew wide as he tried to comfort Sans, to find a leverage point to hold him close again, but he soon realized that it was now beyond that point, Sans was now reaching the climax of his transformation as his body grew bigger. Sans' head now resembled that of his father's "gaster blasters"—as his oldest has called them—and his spine grew sharp needle-like spines that bristled from the bone and all along his tail. His arms and legs stretched out as well, his hands and feet growing until they resembled that of a canine.

When it finally stopped, Sans curled into himself feeling uncomfortable in his new, foreign body. Sans was now roughly the height of his father sitting down, but if he were to stand on his hind legs Gaster wouldn't be surprised if his child was his height, if not a little taller. When it appeared that Sans was no longer in pain did, he scoot closer to his child.

"Sans." When Gaster placed his hand on Sans' skull, Sans flinched and scrambled away, his new limbs uncoordinated from inexperience as he slammed himself into the corner. Sans cried out and Gaster quickly rushed to him. "Easy, easy. It's okay. You're okay, see?" Gaster slowly held his hand out to Sans. Sans' blue and yellow eye burned bright as he watched his father's hand intently, the hole in the carpals a familiar and, oddly, welcoming sight for the frightened blaster. Sans hesitated, his glowing eye shifting between his father's gaze and his hand before he slowly placed it on top of Gaster's outstretched hand. "It's okay, it's okay. The worst is over," Gaster gently scratched Sans' jaw, "you did exceptionally well, my sans-sation."

Hearing his nickname, Sans let out a strained coo, leaning into his father's hand as the scritches relaxed the wound-up blaster.

Then the door was kicked open. "FATHER! SANS! I, THE GREAT PAPYRUS, HAVE RETURNED TO TELL YOU THAT EVERYTHING IS READY!" Sans immediately shrunk back, feeling self-conscious about his scary new form. Papyrus ran over but froze when he got a good look at Sans. "S-Sans?"

Sensing Papyrus' trepidation, Gaster pulled him close to him. "It's okay, Papyrus, you're brother's okay. He's just a little frightened right now."

Papyrus looked at Sans, his eyes shifting from fear to worry as he took in Sans' new form. "W-what happened daddy?"

Gaster gave a small, knowing smile to Papyrus and Sans. "He just went through a growth spurt."

"He's okay now?"

Gaster nodded.

Papyrus looked at Sans, really looked at him, and took in the change. Papyrus was confused…and shocked, and maybe a little scared for his brother, but he trusted his father's words. Papyrus was just happy Sans was doing better and didn't look to be in pain anymore. He took a few steps forward and cocked his head to the side when Sans winced. Papyrus turned to Gaster. "C-can I, can I go and hug him?"

Sans' looked questionably at Papyrus while Gaster chuckled and gave him a sad smile. "Uh, let's give him a little space first, and then we'll see if he's comfortable enough for you to hug him, okay? He might still be feeling sore."

Papyrus smiled and turned back to Sans. "Sans, I'll let you off the hook this one time, BUT you gotta get better! THE GREAT PAPYRUS WILL BE BY YOUR SIDE TO MAKE SURE!"

Gaster chuckled and gave Papyrus a big hug, "You're such a good brother, Papyrus. Thank you for your help."

Papyrus smiled brightly. Sans visibly relaxed and Gaster took this chance to gently grab the big pup and hold it close to him.

The rest of the night was spent in Gaster's room, his large bed able to accompany all three of the skeletons—well, two and one young, adolescent blaster, for the most part. Gaster laid between his two sons, making sure the older one's bristles and claws didn't accidentally cut the little one while they were asleep. Sans was still frightened, and still felt self-conscious about his "sharp" new look (he's gotta write that down later, if he can with his new claws that is), especially towards his little brother, but Papyrus didn't seem to be too put-off by Sans' new appearance. Though he did feel bad he wouldn't let Papyrus hug him at all throughout the night (just in case).

When morning came around, Gaster woke up to find a normal-looking Sans cradling against him, as well as the small Papyrus—though whatever remained of Sans' pajamas left nothing to the imagination. Good thing skeletons don't have to worry too much about getting cold or hot.

He sighed fondly as he rubbed both of his sons' heads. Sleeping in with his boys sounded perfect, but alas, the body of a full-time worker and a single father doesn't know how to sleep-in past 8 am. Quietly, he teleported out of bed and replaced himself with one of the long pillows that were discarded on the floor. Making sure the babybones weren't aroused, Gaster headed downstairs to make breakfast. After the night they had, they deserved a hearty breakfast, especially Sans.

Gaster was already planning to take the day off to spend time with his boys after having such a late work night, but Sans' sudden growth spurt has only cemented the plan further.

Entering the kitchen, Gaster grabbed everything he needed to make pancakes, bacon, and eggs. An hour later, by the time Papyrus came down, breakfast was ready.

"Smells like bacon!" He announced as he marched into the kitchen.

Gaster smiled at the little as he turned the stove off. "Yep, we're having bacon, eggs, and pancakes. Why don't you set the table while I go wake your brother up?"

"Yes sir!" Papyrus saluted as he ran over to the China cabinet.

While Papyrus was setting the table, Gaster walked back upstairs and peeked into his room to see Sans still cradling the large pillow. Gaster smiled as he crept over and nudged Sans. "Sans, my sans-sensation, it's time to wake up."

Sans grumbled something and turned over, his pillow following suit. "nah…too early…"

"I made breakfast; Papyrus is setting the table already."

Sans groggily opened one eye. "don't you have work today or somethin'?"

Gaster patted his exposed shoulder. "I got today off, I wanted to spend some time with you boys after the long night last night."

"oh, ok, sounds cool." There was a pause, and then Sans immediately sat up, his blue and yellow eye glowing. "w-wait. last night…last night…" Sans eye sockets widened. Then, small pinpricks of tears emerged as his face slowly contorted in horror, memories of last night finally becoming clear. "i…was in so much pain…a-and it felt like my bones w-were cracking…a-and then Papyrus came and-"

Gaster pulled Sans into him, hugging the poor skeleton as his son quietly sobbed. "Yes, but it's over now. You got through it, it's never going to be that painful again, I promise."

Sans leaned away so he could stare up at his father in confusion. "w-what do you mean by that? that wasn't just a bad nightmare?"

Gaster gave him an apologetic smile. "Well, son, what you experienced is actually…" Gaster took a deep breath and sighed. "What you experienced was actually…normal."

Sans' look hardened. "what."

"We…we're…oh how do I explain this…" Gaster muttered, turning to the side for the moment as Sans continued to give him a deadpan look.

"y-you're saying what I experienced…that awful, painfulthing I went through last night…was normal?!"

Gaster gave him a sympathetic smile. "I-it's not like I wanted you to experience something like that. Stars, seeing you in so much pain…I-" Gaster paused, his eyes flashing purple for moment before shaking his head. Sans expression softened. "What you went through, I went through when I was your age, and my father and his father and…" Gaster took a deep breath. "The point is…it runs in the family."

"but why? why do we experience this?"

Gaster sighed. The room felt heavy as Gaster placed his hand on his son's. Gaster studied his son's hand compared to his, playing with his phalanges as he tried to formulate the right words. After what felt like ages for the young, anxious skeleton, Gaster finally looked at Sans and gave him the most serious expression he could muster. "Because we're…dragons."

Sans' magic eye faded into nothingness, his face screwed in a mixture of disbelief and confusion. "d-dragons."

Gaster nodded, fighting hard to keep a straight face from his son's reaction. "Yes, descendants specifically speaking."

Sans' gave him a strained smirk. "like the ones in Papyrus' storybooks with the fairies and talking woodland critters?"

It was Gaster's turn to give him a deadpan look. "Come now, Sans, have you looked outside for a minute?"

Sans threw up his hands. "i don't know, dad!" Gaster jumped a little as Sans sighed and shoved his face in his father's chest. "I'm just…overwhelmed."

Gaster held him close again and gave him a skeleton kiss on top of his son's head. "I know, Sans, I know."

"how are we even dragons in the first place?" Sans' voice came as a muffle.

"Genetics, biology…you'd actually be surprised by how many monsters are actually hybrids of other monsters."

"who had the bright idea to screw a dragon?" Sans groaned.

Gaster frowned, not exactly pleased with Sans' terminology, but was quickly replaced with a smirk. "Probably a skeleton." He fired back.

"ha. ha."

Gaster could feel the warmth from Sans' exaggerated breaths in his chest.

He pulled Sans away so he could gaze into his son's tired eyelights. Sans didn't reciprocate and instead looked at his father's chest, where he noticed the claw marks on his shirt. Sans was about to reach and touch the tears when his father's head bumped Sans' on the forehead. Sans froze.

"I'm sorry," His father began, his voice quiet and his body rigid. "I wish I had told you this sooner. I wish I could have at least warned you about the changes you would experience." He rubbed Sans' back as he nuzzled him. "You must have been so scared when it started happening…and I…I wasn't there-" Gaster's voice choked. He stopped rubbing his back and pulled him into a tighter hug.

Sans started shaking, feeling his own non-existent throat tighten up as the moments of his transformation replayed in his head.

It started when he was reading Papyrus his bedtime story. He would get the occasional sharp pain and ache, but he thought it was just his body being tired and crampy. Even Papyrus noticed whenever Sans' voice strained when he felt his body tighten, but Sans told him he was just tired and achy from the day. It was nothing tibia worried about! Papyrus' groan made the older skeleton feel better and the cramping appeared to stop anyways. By the time Sans finished the story and tucked Papyrus in, he was confident he was fine and went back downstairs to watch a little TV before bed.

But during one of his shows, the pain came back, and it was much worse. This time, the pain didn't focus in one area, it spread across his body like a wave, and the cramping pain made Sans reflexively curl into himself. It felt as if Sans moved, the pain would get so much worse. He tried to focus on the TV program, trying to dissociate from the pain, but it didn't work. The pain came and went, like an electric current. During one of the "off" phases, he turned off the TV and hobbled up the stairs, wanting to crawl into bed and sleep it away, only to collapse as the pain returned back into full force. It was at this point Sans started to cry. His breaths became labored as he crawled up the stairs, not caring to turn any of the lights off anymore. When he reached the top, he struggled to his feet and used the banister as a crutch to walk toward his room.

He opened the door and immediately collapsed to the ground. The pain was now consistent, and he could feel his entire body tremble. His teeth chattered and his hands wouldn't stop shaking. He crawled onto his body and curled into a fetal position, his eye beginning to glow and illuminate the room in a chilling glow.

It wasn't long before Papyrus entered his brother's room. He heard the noises earlier, the first time Sans collapsed, Papyrus thought he was just hearing things, the second time…he knew something was wrong. And he was right. When Papyrus noticed Sans' shivering form, he went into protective brother mode. He did everything he could to try and figure out what was wrong and what he could do to help. But Sans didn't want him there, he didn't want Papyrus to see him like this, but all he could do was sob.

Eventually, he asked Papyrus to lock the door. Just in case someone decided to take this time and come in to steal or harm them—that's what he told himself and his brother, but he knew he just didn't want his dad finding out. He didn't want his dad to see him like this and be worried about something else, among the many other things the Royal Scientist has to already worry about.

It would blow over, everything else does.

He never realized how much worse it got until his dad finally got home.

"I'm sorry, my poor Sansy," Gaster's voice brought Sans out of his stupor. "I'm so sorry."

Sans' face scrunched up as tears swelled down his bony cheeks. "no, dad, I'm sorry. I-I should've called or something."

Gaster shook his head without moving it away. "This is not your fault, ok? This is not your fault."

"but it's not your fault either!" Sans hiccupped. "we were ok, just like before. just like all those other times when you worked late too. we were ok-"

Gaster gripped Sans' shoulders hard and looked into his eyes with sheer intensity. "You were not okay!" He yelled, his purple eyes glowing as tears of his own started rolling down his face. Sans froze, his voice caught in his throat. For a minute there, he really could imagine his dad as a scary dragon.

Gaster, realizing what he did, quickly deflated and held him close again. "You weren't okay, and neither was Papyrus." He repeated in a softer tone, craning his head so it rested comfortably on Sans'. "I should have been there."

Sans' melted and leaned back into his father's embrace. He hugged him back this time. "you're here now."

There was silence, but Sans could feel his father relax a little bit. He resumed rubbing Sans' back.

But then a dark thought wormed its way into Sans' skull, and he couldn't help but stiffen. Gaster noticed and stopped rubbing his back. "will….papyrus will have to go through this, won't he?"

Gaster paused. He slowly moved away from his son so he could look at him. Sans returned the gaze this time, but it wasn't any less somber. Gaster nodded slowly. "Yeah. He will." Sans was about to look away when Gaster placed his hand gently on his chin and made him look back at him, a weary, but reassuring smile stretched across his father's face. "But you and I will be here for him."

Sans wasn't completely happy, but he smiled nonetheless. "yeah…" His mind flashed to the moments Papyrus refused to leave his side, no matter how times Sans begged him to. "…just like he was for me."

A loud voice shrieked from downstairs. "WHERE ARE YOU GUYS?! THE FOOD IS GETTING COLD, AND WHILE I, THE GREAT PAPYRUS, HAVE A LOT OF PATIENCE, IT IS NOT INFINITE!"

Gaster cracked up and stifled a laugh. Sans started giggling too, imagining an upset Papyrus stomping his feet while he was wearing his bunny-themed pajamas.

"We should probably head downstairs before Papyrus starts chastising us."

"oh come on that's the best part." Sans eggs, winking at Gaster.

Gaster starts erupting into laughter as he gets off the bed. "d-don't get him too riled up. I want us all to have fun later, ok."

Sans shrugged his shoulders. "no promises."

Gaster feigned an irritated look as he waited for him at the door, watching as Sans sprung off the bed. "but I am curious, what do youlook like as a dragon?"

Gaster gave him a surprised look, not expecting the question out of the blue. But then he smirked. "Like a dragon made of bone."

Sans was taken aback by the teasing answer and frowned. "no, really, I'm serious!"

Gaster's smirk melted into a sweet smile. "I know, maybe one day I'll show you, but right now I don't want to freak your brother out."

"but he saw me last night and he was fine." He whined. "besides, you owe me."

Gaster placed his hands on his hips and looked down at the serious pre-teen. "Oh, I owe you now?"

"you owe me."

Gaster mocked a thinking stance, raising his non-existent eyebrows, before smiling back down. "Alright, I'll show you and Papyrus—"

"Yes!"

"—when your wings grow in."

Sans froze, his smile becoming lopsided. "my what."

Gaster smiled sickly sweet and turned around to walk downstairs. "Sorry Paps, we're coming now."

"DAD." Sans screamed as his eye lights vanished, watching his father disappear downstairs. "MY WHAT?!"