Quick note: there's no real timeline for this series. So…
Sans looked to the left.
No Papyrus.
The right.
Still no Papyrus.
He sighed.
Good. The house was completely empty.
A day of sentry duty, directly preceded by an all-night marathon of schlocky MTTFy movies (a bad idea, he knew, but once he started he couldn't stop), had left Sans in need of a nap. Not just any nap, but at least a good hour or two of solid sleep.
He dragged himself up to his room, stopping only to lock the door. Curling up around a pillow, he closed his eyes. He could almost see the beginnings of a dream flickering before his eyes—something about UltraMettaton EX Sigma Phi vs. The Generic Giant Rubbery Human—when a clatter came from downstairs.
He blinked.
Several times.
"wh…what?"
Without bothering with even the basic formality of putting on slippers, he stumbled out the door.
"bro…what are you doing?" Sans put on his best "completely-awake-and-not-half-dead" face.
There was another clatter, and Papyrus emerged from the kitchen.
"OH, SANS, DON'T YOU LOOK SO AWAKE AND NOT HALF-DEAD TODAY! ON DAYS LIKE THESE, DON'T YOU JUST FEEL LIKE DOING THE DISHES?"
He disappeared around the corner, and the clanging of plates and pans resumed.
"yeah, but…Paps…" He raised his voice to be heard over the din. "PAPS!"
It stopped.
"…can't you be just...y'know…a little quieter about it?"
Suspicion crossed Papyrus's face.
"ARE YOU DOING ONE OF YOUR SCIENCE THINGS THAT REQUIRES LOTS OF ATTENTION AGAIN? ONE OF THOSE THINGS THAT CERTAINLY ISN'T ONE OF THOSE HUMAN DATING GAMES ALPHYS LENDS YOU?"
Sans hung his head. He'd have to hide his borrowed copies of "All-Purpose Sexy Cat Girl Nuku Nuku Naughty~Adventure 3" a little more carefully next time.
"yeah. that's exactly it."
"ALL RIGHT, AS LONG AS YOU DON'T BLOW ANYTHING UP…AGAIN."
Barring one minor incident, Sans couldn't remember ever causing an explosion. He wanted to roll his eye sockets at his brother's TV-acquired understanding of science, but instead turned and trudged back up the stairs.
"oh, my love…please let me sleep" He mumbled something to that effect as he flopped on the bed.
Five seconds later, he groaned:
"OOOOH MY LOOOOVE! PLEASE RUN AWAAAAY!"
Despite his fatigue, Sans felt his eye glowing blue at the robotic screeching from the backyard. Without bothering with even the basic formality of walking down the stairs, he teleported to the back door and opened it.
He wished he could pour bleach in his skull to cleanse his mind of what he saw next. On the roof, directly above him, stood Mettaton, singing some sort of sappy aria.
In a dress.
In his EX form.
"REALLY SAAAAD…YOU'RE GONNA DIIIEEEE…CRY CRY CRYYYYY…SO SAD IT'S HAPPENING."
With a final dramatic trill, the small crowd gathered in the backyard burst into applause. Mettaton gave a curtsy, and fainted dramatically…
…off the roof…
…onto Sans.
"…"
It took everything in his power to assume a cheerful face as his brother rushed over. Well, at least he—
"METTATON, THAT WAS BEAUTIFUL!"
More followed.
"Like, be my husband!"
"Like, no way, be mine!"
"Like, we can share, Bratty!"
"I…I, uh…really liked it…"
"Awesome!"
The smile he tried so hard to keep up dropped.
"well, it ain't over 'til the fat lady sings…"
His brother looked down.
"SANS! WHAT ARE YOU DOING UNDER THERE! WAIT, DON'T TELL ME…" His eye sockets narrowed. "WERE YOU TRYING TO PRANK HIM ACROSS TIME AND SPACE?"
He sighed.
"yeah. that's exactly it."
"Oh, my…" Mettaton blushed. He jumped off of Sans, landing perfectly on his pump-clad feet. "Well, darling, as much as I appreciate your dedication, I can't say I care for your comment about…what was it…the fat lady?"
It was at this moment that Sans's dislike of the TV personality turned to hate. He got up, brushing snow off his shorts.
"yeah. you're kinda made of…heavy metal."
The group surrounding them collectively groaned.
"Hmm. Not quite my genre, but I suppose I can be versatile. Oh, who am I kidding, darling! I'm Mettaton, star of the century!" He leaned in close and whispered in Sans's lack-of-an-ear.
"Listen, darling. I'm a robot. I can TELL you're not exactly…on your feet today."
Ah, good. Someone understood. Maybe he'd get all these people to go away, and—
"And I'm going to make you absolutely miserable for that."
Sans's face turned red from anger.
"Kyaaaah, he whispered something to him!"
"I would trade my SOUL to be him right now!"
"Mettaton…so close…"
"Look! He's blushing!"
He stood up.
"okay, show's over, right? c'mon, maybe you all should…throw a guy a bone."
One more, everyone groaned.
"Well, actually…" Alphys stepped out from the crowd, a box tucked under her arm. "Uh, Papyrus invited us all over because…because…"
"Because Alphy brought over an AWESOME and NOT DORKY card game for us to play!" Undyne flexed her muscles. "It's got SWORDS, and SPEARS, and…"
"AND IT LOOKS AMAZING! AND I, THE GREAT PAPYRUS, SHALL SURELY PREVAIL WITH MY KNOWLEDGE OF ROYAL GUARDING!" He paused. "WELL, AT LEAST WHAT I'VE LEARNED FROM UNDYNE'S TRAINING."
Sans briefly wondered if he could go find some earplugs before remembering his lack of ears. He turned to go back inside…
"Leaving so soon, darling? Oh, come on! The more, the merrier!"
"THAT'S RIGHT! SANS, YOU SHOULD COME PLAY WITH US! ESPECIALLY SINCE YOU HAVE TIME TO PRANK MY FAVORITE SEXY RECTANGLE!"
Mettaton mumbled something about having surpassed the form of a rectangle while Sans tried to come up with an excuse.
"i, uh…"
He had none.
"…one game. I'll kick your tail-bones."
A double-groan was had for the bad pun and terrible excuse for trash-talk.
Notes:
Based on several true stories. Whenever I try to take a nap, the universe conspires against it.
I've been doing some writing, but it hasn't resulted in a lot of visible progress. Bleah.
UltraMettaton EX Sigma Phi is indeed a double reference to Ultraman and Virtue's Last Reward. After a year of trying to play it, I have yet to finish it…but DO NOT SPOIL IT FOR ME, MORTAL, OR I WILL HAVE YOUR H—
Ahem.
On Alphys and Sans's relationship: whoo, this is going to be a long one. But…Alphys makes a remark in the ending if you ask her about Sans that's to the effect of "How do I know him? …Doesn't everyone know Sans?"
Alphy's a bad liar. And that sounds like a bad lie.
I think Sans used to work under Gaster as a Royal Scientist (hence where his mysterious rent money comes from—it's a pension), rather than being his creation. That's just the theory I have—it seems to me that the "but the Skelebros are really his sons" theory, nice though it sounds, just doesn't have enough proof to back it up yet.
Anywho, I support the idea of Alphy and Sans being friends to some degree, since they seem to have been coworkers at some point.