This is another Swap Papyrus oneshot that was requested by UndertaleWeirdo89
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Papyrus stuffed his hands in his pockets as he walked back to his home. Since the monsters had gotten to the surface, everything had been going as well as they'd hoped.
Papyrus and Blue had managed to find a home amongst all of the other former Snowdin residents. It felt just like it had being back in the Underground.
But today... It was almost like a living nightmare. The humans at Papyrus's workplace had been extremely rude to him; calling him names that he didn't even want to speak of and even going as far as to telling him that he shouldn't even be alive at this point in time.
   As if it couldn't any worse, Papyrus had missed the bus and he was forced to walk home in the rain. In the middle of the night. Worst part of all, he could hear the humans around him whispering... Whispering even more hurtful things about him as he passed by.
   He wiped the tears from his eye sockets and stopped for a moment to light his cigarette before pressing it against his teeth, clenching it firmly in his jaw before continuing in his walk home.
   Papyrus pulled up his hood, as if it would tone out the whispering.
   "What a freak..."
   "Looks like that loser missed the bus..."
   "Doesn't that miserable creature have anything better to do?"
   "Look at how terrible he looks. He even goes home like an absolute failure."
   Papyrus pulled his hood down lower, covering up his glowing orange eye. With his free hand, he took the cigarette out of his mouth so that he could let out a puff of smoke before he pressed it between his teeth once more.
   "He should just kill himself now."
   "No one truly cares about that idiot."
   "His brother doesn't even want to work in the same place as him because he's such a useless freak."
   "He should just give up while no one will actually notice."
   The voices continued to harass Papyrus until he finally got home. Once he was inside, he quickly slammed the door shut and slumped against the door, pulling his knees up to his chin as he began to sob.
   He shivered as the cold dampness of his hoodie caused chills to run up his spine. He was so cold... so miserable...
   "Bro? What's wrong? Did something happen at work?"
   Papyrus looked up to see his brother staring down at him, his wide blue eyes filled with concern.
   "No... Everything is fine..." Papyrus lied, wiping the tears from his eye sockets.
   "That's not true and you know it. What's wrong?" Blue pressed, sitting down next to his brother and rubbing his back comfortingly.
   "Don't worry about it... It doesn't matter... Why should anyone care about a freak like me?" Papyrus mumbled, burying his face in his sleeves.
   "Papyrus! You are not a freak! And even if no one else cares about you, I will always care for you! Y'know why? Because I am your brother," Blue insisted, placing his gloved hands on Papyrus's shoulders and forcing him to look him in the eyes.
   The taller skeleton gently pushed away Blue's hands. "Why should someone as magnificent as you care about someone as miserable as me?"
   "Stop talking like that. You are not miserable. You are amazing! Anyone who is lucky enough to be the brother of the Magnificent Sans is most certainly amazing as well!" Blue replied cheerfully.
   "As contagious as your attitude usually is, Im really not feeling it today... I think I'm just gonna go to bed..." Papyrus murmured, the light in his eye sockets dimming as he stood up and slowly made his way up the stairs to his bedroom.
"But you haven't even eaten dinner!" Blue called, his eyes flashing with worry.
"I'm not hungry bro. Maybe later," Papyrus responded before closing the door to his room and locking it.
He looked around at his room, disgusted by the mess all over the floor. There were dirty socks and abandoned hoodies scattered throughout the room, along with crumpled up sheets of paper and empty bottles of honey littering the floor.
"This place looks like a freaking train wreck... How can Sans stand to put up with me every moment of his life?" Papyrus muttered to himself.
His gaze trailed off to the bed, which was equally as messy as the rest of his room. The sheets were in a ball and the pillows were in a pile next to the sheets.
"I guess I should change my clothes before I go to bed. At least my hoodie, anyway..." Papyrus huffed as he slipped his hoodie off over his head and tossed it onto the ground with the others.
He took a moment to stare at the discarded clothing item, self-hate rising up once more at the sight.
What a lazy ass... Can't even bother to keep his damn room clean... No wonder his life is such a wreck...
Papyrus flinched at the echo of the insult in his skull, the comment causing his extreme emotional pain to resurface. He felt tears beginning to form on the corners of his eyes, which it took all of his strength to fight back.
After a few moments, Papyrus went over to his closet and grabbed a clean hoodie from a hanger just inside the door. He slipped it on over his head before flopping over onto his bed.
He stared up at the ceiling, wondering why his life was in such disarray. Papyrus sighed, rolling onto his side and curling up ever-so-slightly before closing his eyes.
After a while, Papyrus found himself deep within a dream. He looked around, eventually finding his brother a short distance away.
"Sans!" he shouted as he ran over to the smaller skeleton.
"Don't speak, you sorry excuse for a brother," Blue retorted, his gaze as cold as ice as he glared at the taller skeleton.
Papyrus stopped dead in his tracks. "Wh-Wha?"
"What even is there to say? You are lazy, irresponsible, apathetic, and you are a freak. I don't even know why I still call you my brother."
"I don't understand..."
"Of course you don't. You never do. Never have, never will. It's never going to change, is it?"
"Sans-"
"Is it??"
Papyrus flinched at the tone of Blue's voice. It was so cold... so empty...
He looked away, not wanting to see the disappointed glare that he knew was completely fixated on him.
   "No response... How typical," Blue growled as he turned away and walked off into the darkness, leaving Papyrus by himself once more.
   "Rejected by your own brother... How much worse could your life get?"
   Papyrus looked up at the sound of the voice he knew all too well. He instantly recognized it as Frisk, the demon that had possessed Chara and caused her to commit genocide throughout countless timelines.
   "Well, guess there's only one thing to do with a failure like you."
   Papyrus closed his eyes, bracing himself for the pain of the knife slashing across his chest. Just as the cold blade of the knife raked across his ribs, he was jolted out of the dream.
   But, the pain from the dream wasn't fading. It still lingered, originally starting as a dull ache in his chest before it progressed into a burning pain in his ribs.
Papyrus stumbled to his feet and teleported downstairs. He fell to his knees as the use of his magic left him completely drained. Blue was alerted by the loud thud of Papyrus falling to the ground, causing him to rush over to check on his brother.
"Papyrus? What's wrong?"
The taller skeleton didn't answer as he managed to get back on his feet and stagger over to the door. Immediately after he got to the door, he doubled over as pain shot through his chest, causing him to grunt in pain.
   "Pap!" Blue shouted as he darted underneath his brother and helped him stand upright.
   "No bro... stop... it hurts..." Papyrus growled, pushing Blue away and leaning heavily against the door.
   "What hurts? If you are injured, then why don't ya let me heal you??" Blue pressed, grabbing Papyrus's hand and pulling him closer so that he could look him in the eye.
   Papyrus doubled over once more as pain shot through him, another grunt of pain escaping from between his clenched teeth, this one slightly louder than the last.
   "Bro... I don't deserve this... Especially from someone as magnificent as you... I'm a miserable excuse for a brother, like you've said..."
   "What? When did I say that? Was this in one of your nightmares?"
   "I don't even know what's real and what's not anymore! It's all the same to me!" Papyrus whimpered, tears streaming down his face.
"Hey, look. We can sit down and talk about this, okay?" Blue offered, helping his brother get to the couch.
Papyrus gritted his teeth as he reluctantly allowed Blue to guide him to the couch, tightly grasping his ribs as pain shot through him once more.
   "I'm so pathetic... so useless... My entire life is pointless... I'm such a miserable wreck..."
   "Papyrus," Blue forced his brother to look him in the eyes. "Stop talking about yourself that way. I don't know who keeps telling you these things, but whoever's doing it is absolutely wrong. You are not pathetic or miserable. You are amazing, just like me!"
   "No I'm not. Stop telling me that. You know it's not true!" Papyrus snapped, his right eye socket flaring with a bright orange flame.
   Blue flinched, instantly falling silent at his brother's sharp retort. Papyrus breathing became more ragged as he dug his fingertips into the couch cushion.
"I'm useless... I'm pathetic... I can't even think straight anymore..." Papyrus mumbled, tears trickling down his cheek bones and dripping onto the soft fabric of the couch.
"Bro..." Blue murmured, resting his gloved hand on his brother's shoulder.
   Papyrus lurched forward, covering his face with his hands to muffle another grunt of pain. He pulled his hood down lower over his face, as if hiding himself from Blue would make everything better.
   "Bro, calm down. I'm here for you. If you wanna talk about this, I'll listen. It's the least I can do to pay you back for being such an amazing older bro!"
   Papyrus shuddered violently as pain surged through him once more. Blue rubs Papyrus's back comfortingly, his eyes dark with concern.
"Useless... Pathetic... Miserable... Careless..." Papyrus mumbled, clearly not focused on anything besides the negative feelings that were flooding over him.
"Bro..."
   Papyrus suddenly lurched forward, falling off of the couch as pain tore through him. He was vaguely aware of the feeling that his entire body was slowly being stretched out. It felt like his bones were slowly being twisted; the agony was horrible.
   It felt like he was about to be crushed. He was also aware of the sensation of something building up within himself; something that he had a feeling he wouldn't be able to contain.
   For a moment, everything was silent except for the beating of his own soul, which was pounding so loudly that he was certain that the entire world could hear it. He was aware of Blue trying to bring him back to his senses, but he was in too much agony to respond.
   Then, chaos struck the once-quiet room. Papyrus suddenly felt his spine begin to snap and twist as it slowly re-set itself. Papyrus groaned in pain, unable to keep himself from giving in to the agony any longer. He felt Blue start to rub his back once more, trying to soothe his pained brother.
   The smaller skeleton froze as he felt something beginning to push against the fabric of Papyrus's hoodie. He looked down, gasping as he realized that the back of Papyrus's faded orange hoodie was beginning to bulge. Eventually, the fabric tore, revealing the massive spikes that had formed along Papyrus's vertebrae.
   Blue shuddered as he heard the sound of bones cracking. He cringed as Papyrus let out a gut-wrenching moan of pain. Papyrus kicked out with his legs, causing Blue to instinctively back away.
   The sickening sounds of bones splintering filled the air as Papyrus's leg structure began to change as well, his feet elongating and the tips of his toes growing sharper. Each individual change was agonizingly slow and extremely painful.
Blue noticed that a tail was somehow beginning to grow from the base of Papyrus's spine. It smacked against Blue's leg, causing him to jump back.
Papyrus's grip tightened on the fabric of his hood, trying desperately to keep it pulled down over his face. Blue realized that the fabric was starting to tear beneath Papyrus's fingertips, which had somehow grown sharper.
Papyrus's moan of pain was muffled by his hood, but the sound could still be heard despite Papyrus's attempts to muffle it. Blue began to notice that the changes were starting to affect the shape of Papyrus's skull; his face had stretched out into a long muzzle and his teeth had grown sharper.
Papyrus's muffled groans were slowly turning into growls, his voice becoming more and more animalistic as the seconds ticked by. Eventually, his sharpened fingertips ripped the fabric of his hood, causing a scrap of orange fabric to fall to the floor.
His hood fell back, revealing his face to Blue. The smaller skeleton gasped as he noticed a large crack that ran from Papyrus's nasal cavity all the way to his browline. He also noticed several twisted horns that had emerged along the back of Papyrus's skull.
"B-Bro??"
Papyrus threw his head back and let out a sound that was more like a roar that a scream of pain. He finally found the strength to stand up, balancing shakily on the balls of his feet. His eye flared with a bright orange flame as orange smoke poured from his maw.
He pushed Blue away as he felt the transformation really begin to hit him. Blue watched in wide-eyed terror as Papyrus dropped down to all-fours, his bones starting to grow longer and thicker as his entire body structure changed into that of a quadruped.
He was becoming so much taller than he usually was. It scared Blue, considering that Papyrus had been the taller one as is, but now... He could crush Blue with a single blow.
   Before he knew it, Blue was staring up at what his own brother had become, the huge beast looming over the smaller skeleton menacingly.
   "Pap?"
   Papyrus shook his head from side to side, as if he were still fighting for control. He snarled ferally, the sound rumbling from his throat like there was a thunderstorm brewing within him.
   "Pap, please..." Blue trailed off as Papyrus stalked closer to him.
   He let out a roar as he lunged for Blue, the smaller skeleton barely dodging.
   "Pap! Listen to me! This isn't you!" Blue shouted, his eyes flaring with a bright cyan-colored light as he activated his magic and held Papyrus back.
Papyrus roared as he thrashed wildly, trying desperately to escape the affects of Blue's magic.
"Papyrus! You have to remember who you are! Please..." Blue begged, the cyan in his eyes slowly fading back to the normal sky-blue color.
Papyrus growled as he continued to thrash.
"Please... You're not this beast... You're my brother... Come on Pap... Just try to remember..." Blue murmured.
Papyrus's growling began to quiet down. His thrashing was gradually growing weaker.
"Come on. I know you can do it. I believe in you," Blue encouraged.
Papyrus rumbled softly, closing his eyes briefly. When he opened them again, they had lost all of their feral gleam.
"Bro?"
"Oh Pap!" Blue threw his arms around Papyrus's foreleg. "I knew you could do it!"
"What happened? Why do I feel so weird?"
   "You got super depressed and all of a sudden, you turned into a huge beast! It was really scary!" Blue explained.
   "...What?"
   "Yeah. You turned into a huge beast!" Blue repeated.
   Papyrus fell silent. He looked down at his hands, the sight of his sharpened fingertips confusing him further.
   "What on earth could have caused this?" Papyrus mumbled.
   "I dunno. But the good thing is that you're okay, right?"
   Papyrus nodded. "You're right about that bro."
   Blue hugged Papyrus's leg tighter. "I'm just glad you're okay. You seemed to be in a lot of pain."
   "Trust me, I feel exactly the same as you. I'm really glad I'm not hurt, or even worse, you. If I'd hurt you, then..."
   "Hey. Don't think about it. Right now, we just need to figure out how to get you to change back," Blue insisted.
   "Agreed. It's weird being like this. The sooner I can change back, the better I'll be."
   "Alright then, lets get to work."

A/N: Omg, I'm so sorry this took so long! I've been running out of time a lot lately because of school. I'll try to get better about updating this, but no promises.
Make sure to leave requests in the comments below! I'm not sure when I'll get the chance to update this again, but for now, stay determined!
-Sora