A/N: Some chapters aren't working and are showing the WIP I did for these fics, I'm hoping this note will fix it and update the problem. Sorry I didn't see it sooner.
~~~~~~TALE~~~~~~

"Sans! I need your help.... could you... come to the living room for a second?" Papyrus asked, seeming unusually shy.

Sans blinked in confusion, putting down the joke book he was reading and rolling off his bed. "yeah, be right there bro." He sighed, but smiled. Whatever his brother needed had to be important for him to call Sans on it.

Sans walked down the stairs step by step, all the way to the bottom until his eyes were met with a very interesting sight.

"Sans? SANS! STOP LAUGHING. THIS IS SERIOUS." Papyrus yelled, an embarrassed orange tinting his face.

"Sorry, bro. I guess I was just having a tail of a time." Sans chuckled.

Before Sans, Papyrus stood nervously with a long tail made of many vertebrae tucked between his legs.

"SANS!"

Sans smiled, attempting to stifle his laughter. "Calm down, bro. It's just a skeleton tail. In a few months it'll fall off or it won't."

"What do you mean by 'it won't'?" Papyrus whimpered worriedly, trying to turn around to see it clearly. Not being able to see it completely, he turned. And turned. And turned.

The skeleton growled and turned faster, eventually giving up on his bipedal dignity and hopping to all fours to get a good look at his tail. He even tried barking at it like how some of the royal guardsmen do when they chase stuff.

Sans covered his mouth roughly, trying his best not to laugh at the sight of his younger brother chasing his own tail like a dog monster. "I mean that it will just stay there."

Papyrus lost his footing and careened into the shelf Sans' dear pet rock lives. Dazed, he shook it off and got up as quickly as he could, which prooved to be a mistake as he fell forward onto his face. "Wh? What do you mean 'it will just stay there'?"

Sans shrugged off his hoodie and turned around. "It just will." Between his shirt and shorts a little tail wagged.

Papyrus gasped loudly. "SANS! Why didn't you warn me? Truly you had known that this would happen. NYEH HEH HEH."

Sans shrugged. "I wasn't sure if you were going to get one or not. We are the only skeleton monsters we've met."

Papyrus nyehed thoughtfully as he rubbed his chin. "Once again your logic troubles me, brother."

Sans couldn't hold in a giggle as his brother's tail wagged subconsciously.

~~~~~~ swap! ~~~~~~

Papyrus shot up in the air and turned around violently when he felt something grab his newfound tail. "Hey!" He yipped.

His brother Sans stared at the empty space in his hand that used to occupy a tail. He looked up to see his younger brother covered in an orange blush and nearly laughed. "Heya Papy, what you got there?"

The taller of the two sighed as he let himself relax. "I... I don't know? It just sort of appeared a few days ago and I've been trying to hide it..."

Still smiling and admittedly entertained, Sans scratched his head. "A few days? I have no idea how you managed to keep it away from the magnificent Sans so long... I mean, I am magnificent. Speaking of long... YOUR TAIL, BROTHER!"

The blue clad skeleton reached for it, but the vertebrae flinched away instinctively. Sans pouted and Papyrus couldn't help but smile. "Hands off the merchandise, bro."

Sans rolled his eyes. He hopped down on all fours and stood with his body low and crouched. Papyrus flicked his tail nervously. "Uh, what are you doing?"

Sans shot his brother a mischievous look. "What's it look like?"

Papyrus smirked. "Looks like you're observing me with great de-tail."

Instead of getting the reaction he was expecting, Sans smirked. "It would be easier..." suddenly, he pounced. His legs thrusted himself forward as he reached for his brother's tail. Papyrus lurched back in surprise, doing nothing to delay or stop the inevitable. His tail was caught by his big brother. "If you weren't so attached to the darn thing! Mwheheheh!"

Papyrus laughed, pride beaming off of himself. He stopped in realization. "Hey bro... any idea on what this is exactly?"

Sans snapped to attention. He immediately smiled in a comfortable way. "Oh don't worry. It's just your skeletail. I have one too!"

Papyrus froze. "Wait, what?"

~~~~~Underfell~~~~~~

"SANS!" A distinctly angry yell clashed against the walls of the house and Sans flinched.

"Yeah, Boss?" He said, clambering out of his room.

Immediately he was pushed backwards by the chest and he fell heavily with a loud "oomph". Above him was Papyrus, one hand pressed painfully against his chest. He must've been putting his weight into it...

"B-boss?" Honestly afraid for his life, Sans stared at his younger brother with large frightened eyes. The weight on his chest got heavier and his breathing became labored as his ribs were pressured above their limit. Papyrus snarled, teeth bared and his eyes watching Sans back... empty. Sans whimpered and Papyrus ripped himself away before blinking stupidly.

"WHAT IN GOD'S NAME WAS THAT?" Papyrus shouted.

The smaller of the two watched with confusion, eyes assessing the situation. "Is... is there anything wrong? Papyrus?" He noted how his brother's eyes reverted back to normal. God, his bro had looked animalistic before hadn't he?

"YES! EVERYTHING IS WRONG. I WAS ABOUT TO SNAP YOUR NECK IN HALF AND TEAR YOUR BONES APART ONE BY ONE WITH MY MOUTH. WHY DON'T YOU EVER DEFEND YOURSELF?" Papyrus raged, eyes flashing between going empty with anger and dimly lit with control.

"You were about to... what?" Sans blinked, still confused and still scared.

Papyrus stopped and took a relaxing breath. He stared his older brother dead in the eye. "Sans."

With an unchanged expression, Sans replied. "Y-yeah, Boss?"

Papyrus blushed as he turned around. Still confused Sans stated silent. His brother sighed angrily at the lack of response. "WELL?"

"Well what, Boss?" There was suddenly a movement. Below the back of Papyrus's knees. Sans' eyes widened as a long bone tail twitched in annoyance. A smile crept proudly against Sans' face as he stood. To say Papyrus was surprised to see his brother smiling and among tears was an understatement. Sans laughed at the reaction he got and calmed himself enough to speak. "It's about time your tail grew in. I was getting worried it wouldn't."

"Worried...? About time...? You... YOU KNEW DIDN'T YOU? IS THIS SOME KIND OF PRANK?" Papyrus barked.

Sans broke into a sweat. "Prank? Oh god no. I know you hate those, no. I swear, boss. This is natural, I have one too!"

Sans was brutally pushed to the floor.

"I DON'T BELIEVE YOU."

Sans scrambled back up and took a few steps back. His brother fell onto all fours and began growling. Immediately deciding it was his best bet, Sans jumped off the second floor balcony into the living room. The taller skeleton snarled and jumped after him, surprisingly agile as a quadruped.

Sans spent the entire day getting his cardio in as he ran from his brother, only to eventually give up before passing out and showing him his tail. Papyrus was not impressed.