Gaster Blaster Transformation Oneshots (ON HIATUS)

The Truth Hurts, Doesn't It?

   This one is Underfell Sans and was requested by izz2772
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Sans closed his eyelids as he drifted into sleep. He had just begun to fall into slumber when he heard heavy footsteps across the clearing. He flinched as he heard the sound of his boss's voice.
"Sans! What the hell are you doing?! Get up now!"
Sans growled angrily as he sat up at his sentry post. "It ain't your job to watch me, y'know."
Papyrus stomped towards his brother, reaching forward and grabbing the golden chain dangling from Sans's spike choker. The smaller skeleton gagged as he clawed at his choker.
"B-Boss please... P-Put me down..." Sans pleaded, a desperate gleam in his glowing red eye socket.
The pinpricks of red light in Papyrus's eyes glinted with pure hatred.
"Don't ever speak to me like that again," Papyrus hissed, his grip tightening on Sans's choker.
Sans gasped for air as sweat began to form on his forehead.
"Know your place, freak," Papyrus spat, throwing Sans back down onto the ground.
The smaller skeleton grunted as he hit the ground with a loud thud. He coughed as he held a hand to his neck, relieved that he could breathe once more.
Sans tried to stand up, his legs shaking as he grasped at a nearby tree for support. He expected that the shaky feeling would go away after a few moments. But it didn't. Instead, it grew worse and worse. He clutched at his skull with his free hand as a sudden migraine came over him.
He was aware of Papyrus staring at him with anger in his eyes.
"Come on. You're being ridiculous. I didn't hurt you that bad," Papyrus growled.
Sans gritted his teeth, shaking his head as if the sudden headache would go away if he did so. He felt feverish and dizzy, forcing him to lean heavily against the tree.
He started to take off his jacket, hoping that it would stop the overwhelming feverish feeling from getting any worse. It didn't help at all. It only seemed to be spreading all throughout his body.
His breathing grew heavier and more ragged as a burning pain began in his chest. The pain began to rapidly spread through Sans's body, making it extremely difficult to stay on his feet.
Eventually, Sans lost his balance and collapsed in the snow. Papyrus stomped over to him and grabbed the chain attached to Sans's choker, attempting to yank the smaller skeleton to his feet.
"Get up, you lazy ass. I don't know what you think you're doing, but it's not funny. You are being ridiculous," Papyrus hissed.
Sans clawed weakly at his neck, trying to free himself from the taller skeleton's grasp. Papyrus had lifted his brother into the air and was gripping the collar of Sans's shirt, leaving the smaller skeleton's legs dangling in the air.
Suddenly, a wave of pain overtook him, causing him to grunt as he kicked out with his legs. Sans dug his fingertips into his brother's arm as he desperately tried to force him to let go.
Papyrus growled at his brother's actions, tightening his grip on the collar of Sans's shirt in anger. Suddenly, Papyrus felt a sharp pain in his arm, causing him to drop Sans and clutch a hand to his forearm.
He was surprised to see a smudge of blood on his arm once he removed his gloved hand from the injury.
"What the..." Papyrus trailed off as he looked closer at Sans's fingertips.
That was when he realized that the smaller skeleton's fingertips had grown sharper. Sans shuddered violently as another wave of pain overtook him, forcing another grunt out from between his clenched teeth.
Papyrus heard the sound of bones cracking, causing him to flinch. God, was his brother seriously taking this as far as trying to break his own bones? He really was ridiculous.
But the taller skeleton trailed off in his thoughts as he realized that Sans wasn't trying to break his own bones. His bones were actually... changing?
Papyrus shook his head, making sure that he was seeing things correctly. Sans let out a pained groan as his spine began to snap and twist as it re-set itself. Massive spikes had begun to form along Sans's vertebrae, eventually ripping through the red fabric of Sans's sweater.
Another spine-snapping convulsion wracked Sans's body, forcing another groan out from between his clenched teeth. Papyrus realized that his brother had somehow begun to grow a tail.
Sans screamed in agony, throwing his head back as his glowing left eye flared with a bright red flame. His face was beginning to elongate while several horns began to emerge along the back of his skull.
   Sans let out another cry of agony as his feet began to change as well. His feet seemed to elongate as the tips of his toes grew sharper.
   The smaller skeleton's voice was slowly becoming more animalistic as the minutes dragged by. Papyrus stood back and watched as the transformation finally came to an end.
   The huge skeletal beast that stood before Papyrus let out a low snarl as he stalked towards the other skeleton. Red smoke poured from the beast's massive jaws as he approached the once-taller skeleton.
The only reason Papyrus ever felt like he was the one in charge was because he was always the tall one out of the two of them. But, now that his brother had turned into this huge beast... It made Papyrus feel like he wasn't in charge anymore.
It's hard to intimidate someone when they're practically looming over you.
   Papyrus felt so small... weak...
   ...hElplEss...
The huge beast let out a fierce roar as he threw himself at his own brother. Papyrus barely had time to dodge as the beast pounced directly where he had been just moments before.
   The beast's feral red eye tracked down Papyrus's movements, much like a predator tracking its prey. It wasn't long before he pounced once more, barely missing Papyrus by mere inches.
   "Snap out of it! I am the Boss here! Not some fucking moron like yourself! Get ahold of yourself!" Papyrus shouted, summoning a few bone attacks and launching them at the beast, the sharpened tips doing nothing to harm the huge creature.
The beast roared, rearing up on his back legs before slamming his clawed hands back down onto the ground, sending snow flying all over the place.
"Listen to me! Pull yourself together!" Papyrus snarled.
He called upon the powers he knew were within himself and summoned a gaster blaster. He aimed the floating skull at the massive beast, his eyes blazing red in the dim light of the forest.
A beam of red light burst from the floating skull's mouth, hitting the massive beast straight in the chest. The creature stumbled backwards, shaking his head violently from side to side.
   He stood there for a moment, his eyes squeezed shut. When he finally opened them, his single glowing red eye had lost its feral gleam.
   "Bosssss? What happened?"
   Papyrus growled under his breath. "You went insane and tried to attack me."
   Sans snorted. "You probably deserved it anyways."
   "What makes you say that?"
   "You're always such an ass hole. Someone had to teach a lesson, didn't they?"
   "Not really. I am above you. Don't think this justifies your actions," Papyrus retorted.
   "Whatever."

A/N: This was fun to write.
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Stay determined!
-Sora