Gaster Blaster Transformation Oneshots (ON HIATUS)

Like Father, Like Son

Ok, this wasn't a request, but I just wanted to write a oneshot for baby bones sans. Also, I will be including some Dadster au in this. Cuz it's cute. :3
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"D-Dad?"
Gaster looked up from his notebook to gaze at his son. "What's wrong Sans?"
"I-I dunno... Everything h-hurts..." Sans cut off with a grunt as he doubled over in pain.
Gaster rushed to his son's side, a look of concern in his eye sockets. Sans lurched forward, clinging onto the sleeves of his father's lab coat.
Sans shuddered violently as another wave of pain overtook him. Gaster put a hand on the child's shoulder, closing his eyes as he fought back tears from the sight of his son suffering.
   His eyes snapped open as he heard the sound of bones cracking. He looked down at Sans, who had a hand tightly grasping the fabric of his worn-out hoodie where his soul would be.
Sans let out another grunt, this one louder than the first. Gaster's soul pounded as he stared down at his son in disbelief. Another spine-snapping convulsion wracked Sans's body, causing Gaster to flinch.
   That was when he realized that Sans's spine was beginning to snap and twist as it re-set itself. Massive spikes were beginning to form along the small skeleton's vertebrae, forcing a stifled scream out from between his clenched teeth. Eventually, the back of Sans's hoodie tore open as the spikes continued to grow.
   Gaster swore that he'd felt his soul skip a beat as he realized that Sans's teeth were growing sharper.
   "Oh no... This is bad..." Gaster mumbled, his eyes going completely blank.
"Wh-What's going on? What's happening to me?" Sans asked, his voice strained.
   "This shouldn't be happening to you... I didn't think it would be passed on to you..."
   "What do you mean? What was passed on to me?" Sans cut off with a wail as pain shot through him once more.
"Oh no... What if Pap has it too? How did I fuck up this badly?!" Gaster growled to himself, digging his fingertips into his own skull.
"Dad, n-no... You didn't screw up..." Sans insisted.
"Yes I did!" Gaster dragged his hands down his face, leaving slight marks on his skull as the tips of his fingers grazed the surface. "I should have known this would happen!"
Sans reached up to tap his father's shoulder, but before he could touch him, a jolt of pain through the lower half of his body made him draw back with a grunt.
The young skeleton's feet were beginning to elongate and the tips of his toes were growing sharper. A tail was beginning to grow from the lower portion of his spine. He could feel his bones shifting and growing, his body drawing on a mass that it didn't normally have.
Several curved horns erupted from the back of the small skeleton's skull, forcing a cry of pain out from between his teeth. His face was beginning to stretch out into a long muzzle.
   By the time the transformation had ended, the once-small skeleton had become the size of a large dog. Gaster finally pulled himself out of his thoughts, taking a moment to take in the sight of what his son had become.
   He reached out and rested a hand on Sans's muzzle. "It's okay Sans. I'm here for you. I'm sorry that you've had to go through this."
   Sans blinked, his glowing blue eyes staring at his father. "What do you mean?"
   Gaster took a deep breath. "You know that one time I told you that I was going to see King Asgore? And I didn't come back for a week?"
   Sans nodded. "What about it?"
   "I wasn't actually going to see Asgore. Believe it or not, I was just trying to get away from everyone else so that... well, I wouldn't hurt anyone when this happened," Gaster explained.
   Sans looked confused. "Soo... You mean to tell me that you've had to go through what I just did before?"
   Gaster nodded solemnly. "It's been happening to me for as long as I can remember. I was worried that you two might inherit that 'condition', and I guess I was right..."
   Sans fell silent, a distant look in his eyes.
   "I wouldn't be surprised if Paps is capable of it as well."
   "Will it always... hurt like that?" Sans asked hesitantly.
   Gaster paused for a moment. He knew that his son wouldn't like the truth very much.
   "Unfortunately, yes. I've tried pretty much everything to get it to stop hurting like that, but nothing works. I guess you just get used to it after awhile," Gaster said finally.
   Sans's eyes went dark. "Good to know. Will I get any sort of... warning before it hits?"
   Gaster shook his head. "Not really. It usually starts off small, which is your cue to get away. Once it really starts to affect you... there ain't no running after that point."
   "What if Pap finds out? What do I tell him?" Sans asked.
   "To be honest, I'm not sure. If you wanna keep him innocent, then I'd suggest just staying alert for any signs that it might happen and get away from him as soon as you can. Honestly, there's no harm in just telling him beforehand," Gaster answered.
   "What if it happens to him? What do I do then?"
   "Stay with him the whole time. Help him through it. If you want, I can try to figure out a way for you to contact me should this situation happen to arise."
   Sans nodded. "Thanks Dad. That would be helpful."
Gaster smiled. "Anything for my precious son."
Sans ran over to his father and threw himself into his arms, putting his own arms around Gaster's neck in a hug. "I love you Dad."
Gaster grinned. "I love you too Sans."

A/N: Awww! So fluffy!
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-Sora