Okay, this is gonna start with partially-transformed blaster sans. This was requested by izz2772
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   Sans stared up at the stars, the tip of his tail twitching idly. He wished he wasn't stuck like this.
   This whole thing started when that group of humans had attacked Papyrus. Sans had found his brother, battered and weakened. He couldn't even walk on his own.
   Sans had been outright pissed. It was to a point that he'd started transforming. He couldn't recall much else, but all he could remember was being pulled out of it by his brother's desperate pleas for him to stop.
   Now, usually, he would change back at that point in the transformation. Problem was, for some reason, he didn't revert back to his usual appearance. Hence why he had been stuck in partial blaster form for at least a week now.
   He sighed and flopped backwards onto the grass. He looked up at the full moon, taking a moment to really take in its beauty for the first time in awhile.
   Sans's tail thumped against the ground, which annoyed him since he felt as though the damn thing was utterly useless other than to give an unwanted indication of his mood.
   "Maybe if I try to shift again, this won't be so bad..." Sans thought aloud.
   He took a moment to consider the idea. "But what if it goes wrong and I lose control? I'm not in the Underground like I usually am when I do these things..."
   He clicked his teeth together, annoyed by the way his sharpened teeth pushed up against each other and made his jaw feel way too tight.
   "Screw it. Why don't I just test it out to see what happens? It's not like I'm around a bunch of people anyways."
   Sans took a deep breath and tried to relax. He closed his eyes as he reached into the depths of his own mind to call out the beast within himself.
   Once he'd found it, he made sure to take off his jacket before attempting what he was about to do. He exhaled slowly as he prepared to unleash the beast inside him.
   He tensed as pain suddenly struck him, causing him to cry out. Immediately, he knew there was something wrong with this particular transformation. Something about it seemed... off... Usually, the pain would start out dull and then grow worse and worse as the transformation affected him more and more.
   But this time, the extreme pain that he only felt when the majority of the change was really starting to affect him had hit him right from the beginning.
   "Oh god... It hurts... It hurts so much..." Sans whimpered.
He rolled over onto his side, gasping as pain surged through him once more. He felt his tail coil around his leg as he curled up into a ball. He panted heavily, unable to ignore the growing pressure on his bones.
   He moaned in agony as he felt a jolt of sharp pain in his chest. That was when he began to realize that nothing about him was actually changing. It was like he was... stuck. Stuck having to deal with the intense pain of a transformation, yet nothing was happening.
   He groaned as pain surged through him, tucking his face further down into the collar of his t-shirt as if it would hide his pain.
"P-Papyrus... S-Someone... Anyone... Please... Help-" Sans cut off mid-plea with a cry of agony, his left eye socket blazing with icy-blue flames.
He dug his sharpened fingertips into the fabric of his shirt as he clawed desperately at his own ribcage. He barely noticed that his fingertips were piercing through the fabric of his shirt and leaving huge gouges in his ribs over the indescribable pain throughout his entire body.
   "Help... Please..." Sans murmured, his voice strained.
   He weakly managed to roll over onto his ribs, still tightly grasping his chest with his arm. He panted heavily, the painful cramping in his bones preventing any further movement.
Sans reached towards his jacket, which was lying a few feet away. He finally managed to grab the discarded clothing item and shakily reach into one of the pockets. He pulled out his cell phone and dialed Papyrus's number with trembling hands.
He sat up, still hunched over due to the horrible pain in his bones. He held the phone up to the side of his skull and waited for Papyrus to pick up.
"Sans? What's wrong?"
   Sans choked down a cry of pain. "Pap, I need you to come over here..."
   "What's the matter? Are you hurt?"
   A grunt of pain finally managed to escape from between his clenched teeth. "I-I'll explain when you get here. Just hurry up..."
   "Slow down. Where are you exactly?"
   "In the woods behind the house... I'm sitting on the second hill from the house..."
   "Okay, I will be there as soon as I can be."
   A sudden jolt of sharp pain through his ribs caused him to lurch forward with another grunt of agony, this one slightly louder than the last. Sans dropped his phone, not even getting the chance to hang up.
   "Please hurry..." Sans murmured, his voice hoarse and shaky.
He tried to relax, but the pain in his bones prevented this from happening. He felt sweat begin to trickle down his skull as he strained to keep himself from crying out in agony.
It felt like ages before he finally picked out the sound of heavy footsteps coming towards him. He could faintly hear the soft sound of his brother panting as he ran as fast as he could towards Sans.
"Brother! What's wrong?!" Papyrus exclaimed, kneeling down beside his brother.
Sans gritted his teeth, trying not to cry out in pain.
"It's okay. I'm right here," Papyrus murmured, carefully picking up his brother and holding him close to his body.
"Bro... I-I can't..." Sans trailed off, shuddering as pain wracked his body once more.
"Can't what? What's going on?" Papyrus pressed.
Sans screamed in pain, digging his sharpened fingertips into Papyrus's arm. Papyrus winced, but fought down a cry of pain.
"I-I tried to t-transform again, but I couldn't- NNGH!" Sans's sentence broke off with a grunt of pain.
"What do you mean 'you couldn't '? Why can't you transform?"
"It feels like the transformation is actually happening, but it's not... I c-can't do it..." Sans whimpered.
"Of course you can. You just have to believe in yourself," Papyrus encouraged.
"B-But it's gonna hurt..." Sans whined.
Sans let out a groan as he felt another wave of horrible pain tear through him.
"It's okay. The pain will only be for a few minutes. I'm here for you, okay?" Papyrus murmured.
Sans moaned in agony as he felt the pressure on his chest grow heavier. If it weren't for the fact that he was fading in and out of consciousness, he would have heard the sound of his bones creaking.
Papyrus flinched at the sound. The transformation was beginning.
"Pap... It hurts... B-Bro, I'm scared..." Sans mumbled.
Papyrus twitched as he felt Sans's tail coil around his leg, but he said nothing. He tightened his grip on his brother's trembling body, determined not to let him go.
"It's okay. I'm here. Don't fight it," Papyrus whispered.
"Pap- HRNGH! I c-can't... I've made a mistake! I don't wanna change anymore! I just- NRRGHH!!" Sans's cries of distress were becoming louder, his voice becoming more and more animalistic.
"Shh... It's okay. You're going to be alright," Papyrus attempted to soothe his pained brother by gently stroking Sans's skull with his gloved hand.
   "Please... Make it stop..." Sans murmured, his voice strained.
Sans groaned in agony as pain seared through him once more. Papyrus flinched as he heard the sound of bones popping once more. He tried not to focus on his brother's transformation, but this was difficult, since he couldn't exactly tone out Sans's cries of pain and the sickening sound of bones cracking.
Sans let out a gut-wrenching moan as pain surged through his chest. Papyrus could feel Sans's body drawing on a mass that it didn't usually have. Though he wasn't really looking at Sans, since witnessing a transformation was still scarring for the younger skeleton, he could tell that it was happening.
Sans kicked out with his legs, the sharpened tips of his toes digging into the soft grass beneath him. Out of the corner of his eye, Papyrus could see that the structure of Sans's legs were slowly changing, even more so than they previously had.
The sickening sound of bone splintering caused Papyrus to flinch. He felt nauseous just thinking about what was happening.
He began to notice that Sans's voice was gradually deepening and becoming increasingly animalistic. Papyrus squeezed his eyes shut, clearly not wanting to be there, yet so determined to help his brother that he couldn't help but stay.
Eventually, Papyrus felt Sans pull away from him, causing his attention to be reverted back to his suffering brother. As soon as Sans had pulled away, the transformation really started to kick in.
Sans groaned in agony as his spine began to distend, the sounds of his bones cracking and popping muffled by the fabric of his t-shirt. Massive spikes were beginning to emerge from his vertebrae, eventually tearing through the fabric of his shirt.
His ribcage began to expand, while his face stretched out into a long muzzle. Horns erupted from his skull, forcing stifled screams out from between his clenched teeth.
After several horrifying minutes, the transformation ended. Papyrus looked up at the massive beast, scared for a moment that he would attack him. But he didn't.
   Sans's breath was still coming in ragged gasps, but his breathing was gradually becoming more steady as the lingering traces of the transformation faded.
   "B-Bro?"
   Papyrus darted forward and hugged his brother's massive skull. "See? I knew that you could do it."

A/N: Holy sh*t guys! I'm so sorry for such a big delay! Like I mentioned in the previous update, I got a bit of writer's block and I lacked inspiration for this. :/
But, that all aside, once I got over my damn writer's block, this was really fun to write!
Thank you all so much for your patience on these updates! And for now, stay determined!
-Sora