Person A's been sitting there for a while waiting for a date that never showed when Person B sits down and offers to be their date instead.
The idea that started it all! Inspired by a Kustard fic I can't find anymore, but it was really cute and had way too many puns. Far more than I can do.
Fun fact: I used my own phone's actual predictive text for that one sentence. It was amazing and I love it!

Sitting all alone at booth in the corner of a quiet, homey pub, Sans pulled out his phone and checked the time. Half an hour since he was supposed to meet the blind date his brother had set up for him, and that wasn't even including the extra ten minutes early Papyrus had forced him to be! Sans wondered if half an hour was long enough or if he'd have to wait longer before Papyrus let him give up on a date that was never going to show. Not if Sans had any say in the matter. Phone still in hand, Sans opened up the most recent messages and started typing.

*no1s shown up yet bro u sure u got the rite date and tiem?

YES, I'M SURE. VERY SURE! AND THEY STILL HAVEN'T SHOWN UP?

*nope juts sittin here all a lone

YOU'RE AT THE HAWKINS PUB AND KARAOKE, CORRECT?
I CHOSE IT BECAUSE I KNEW YOU'D LIKE THEIR AWFUL FOOD.
AND IT'S STAND UP NIGHT.

*yeah, sure, the hawk pub bar plaec
*been sittin heer 4 45min now

BECAUSE I JUST TEXTED YOUR DATE AND THEY SAY THEY ARE THERE AND DON'T SEE YOU.

*huh. tel em 2 look round a little may b we jus missed eschother
*i akm p short may be they thot i'd be tol like u
*or missed me in the cloud
*crowed
*drown
*crowd
*damn autocorrect

SANS I KNOW YOU HAVE AUTOCORRECT TURNED OFF.
JUST STAY WHERE YOU ARE.
UNLESS WHERE YOU ARE IS HIDING OUT OF SIGHT, IN WHICH CASE YOU HAD BETTER GET OUT WHERE YOU CAN BE SEEN. AND THEN STAY THERE SO YOUR DATE CAN FIND YOU.

*taht hurts bro. i'm siting a table like a gown up

GOOD, THEN STAY THERE.

Sans waited, but no new texts appeared. Seems Papyrus was coordinating with the blind date to make sure they found him. Good luck with that. Sans tucked his phone back into his pocket and rested his skull on his hand, he heaved a sigh and drummed the fingers of his free hand against the table. He'd probably have to ride out the full hour before Papyrus would allow him to call the whole thing a bust and go home.

"Looks like someone's going to be in the dog house tonight."

"huh?" Sans looked up to see a fire elemental sliding into the seat across from him. He sat back and looked the guy up and down.

"I was sitting at the bar and couldn't help but notice you've been sitting here all alone for quite a while."

"heh," Sans shrugged and slouched comfortably into his seat. A little conversation wasn't a bad way to waste the last twenty minutes before his brother would let him leave. "blind date's nowhere in sight. but you see i'm not all that disappointed, can't say eye was looking forward to it."

The fire elemental snorted, and Sans couldn't help the grin that spread across his face. "Those were all awful, I don't think that last one even counted as a pun." The crack across his face looked too much like a smile for Sans to take the comment seriously.

"the name's sans," he held a hand out to his new friend.

"Grillby," he reached out to take the offered hand. The long, drawn out, wet sound of a fart started to play, but Grillby's hand flared and the sound suddenly cut off.

Sans pulled his hand back to look at the melted piece of rubber hanging limply from it. "no need to get so fired up, it was just a little spark of a joke."

"I regret taking pity on you already."

Sans's grin only spread wider, if the guy really regretted it he'd have gotten up and left. He must have a dry sense of humor. Sans leaned on his elbow as he turned that grin on his new blind date. "so we know why i'm here, what's your story hot stuff?"

"I own a bar and grill on the other side of town, sometimes I like to go visit the competition and check them out."

"i see, a little corporate espionage."

"Nothing like that," Grillby shook his head and held up his hands as if afraid someone really would accuse him of that. "I just like to see what they offer, compare prices, see what the atmosphere's like. It's important to keep up with the competition."

"nah, i get it, that's pretty cool. say, been to a place called hawkins? this side of downtown?"

Grillby grimaced, "Once or twice. Their drinks are overpriced and the karaoke always gives it a… an uncomfortable atmosphere. At least I don't find it that comfortable, too noisy and distracting."

"yeah, all that off key singing. though i hear tonight it's stand up."

"Why go there when I can hear all the bad jokes I want right here?"

Sans gasped and clutched a hand to his ribs in mock offense, "i'll have you know those were my best awful puns!"

Grillby chuckled, "Surely not your best, you can do way worse than that."

Sans thought his face was going to split in half from the grin spread across it. "alright, alright… gimme a second. my worst jokes? let's see…" Sans hemmed and hawwed for a minute as he thought up a few jokes. "okay, got 'em. is this a blind date? if not, it will be because i'm staring at the sun. do you have 11 protons? because you're sodium fine. are you an omelet? because you're making me eggcited. is that a mirror in your pocket? 'cause i can see myself in your pants. your face…" Sans paused for effect but never finished the joke because Grillby was sprawled over his side of the table, laughing uncontrollably.

"Are you finally ready to order?"

Sans looked up at the waitress who was smiling down at them, though the strain at the corners of her lips meant she was trying very hard to hold back a wide grin. Not that she needed to, Sans's was wide enough for both of them.

"nah, i think he needs a minute to calm down first."

"Sure thing, I'll be back to check on you shortly."

Sans nodded to let the waitress know he heard her, then went back to watching Grillby slowly calm down. Once he gathered himself together, Grillby sat up and self consciously straightened out his shirt.

"infinite universes, eight planets, one sun-" Sans started.

"Wait," Grillby interrupted, "aren't you going to finish the joke you were about to tell?"

"and not finish this one either?"

"My apologies," Grillby leaned forward with a smile like a glowing crack in hot magma across his face, "please continue."

"one sun, seven billion people, and i get lucky enough to meet you."

"That was surprisingly sweet."

"oh, was it? heh…" Sans nervously scratched the back of his skull. Before he could say anything else his phone buzzed and let out a jaunty little jingle. "oh, sorry, that's my bro's ringtone, i should probably get that." Sans sheepishly pulled his phone out to see that Papyrus had sent him more texts.

WELL, IT'S BEEN AN HOUR SINCE YOUR DATE WAS SUPPOSED TO START.
I SUPPOSE YOU ARE FREE TO GO, YOU HAVE BEEN MORE PATIENT THAN I EVER EXPECTED YOU TO BE.
THOUGH YOU MAY HAVE JUST BEEN TOO LAZY TO GET UP.
SIGH. IF WE ARE REALLY, REALLY LUCKY YOU'LL BUMP INTO EACH OTHER ON THE WAY OUT. I REALLY THINK YOU'D LIKE THEM, SANS.

*thats sweet bro but eye cant leav now, wat wud my date think?

WHAT DATE? THEY JUST SENT ME A TEXT SAYING THEY'RE LEAVING?

*well some1s sitting w/me
*name's grillby, he seems rly nice
*laffed all my jokes s fur
*were halving a bowl

YOU'RE BOWLING? SANS! I THOUGHT YOU WERE AT THE HAWKINS PUB AND KARAOKE!

*sry, ment ball
*dam autocorrect

SANS WE BOTH KNOW YOU PURPOSEFULLY TURNED THE AUTOCORRECT OFF.

*well let me jus trn that n the prdictiv text bak on
*There, I have a few questions about the stood up and rolls and a half the time I don't have to be there at least the first time.

WAIT, STOP! THIS IS AWFUL? AND SOMEHOW EVEN WORSE? ? ?
ALSO I WANT TO HEAR ABOUT THIS DATE YOU ARE ON? ? ? ? ? WHO IS THIS GRILLBY?

*i won't fnd out til eye sit n talk w/ him
*get 2 no him
*isnt that wat dates r 4?

FINE, BUT I WANT TO HEAR ALL ABOUT IT WHEN YOU GET HOME!

*sure thing bro. luv ya