A request done for my BFFF (best fanfic friend forever) GoldGuardian2418! Enjoy, Amiga!

At the home of the skeleton brothers, Sans and Papyrus, Frisk the human girl was giggling to herself as she hid the last bottle of ketchup.

A few hours later,

"WHERE'S THE KETCHUP?!" Sans the skeleton came running into the living room where he found Frisk calmly watching TV.

"What's up, Duncle?" asked Frisk, tiling her head up to see Sans.

"We're out of ketchup! Where's the ketchup?!" Sans fretted, clutching onto his hoodie and jumping around.

"There's no more in the house." Frisk answered as she changed the channel.

"WHAT?! NO MORE KETCHUP?!" Sans was in full-on panic mode. "I gotta find some!"

He ran off in search of the coveted condiment while Frisk giggled to herself.

Sans began tearing the kitchen apart. He rummaged through the fridge, kitchen cabinets, he searched though everything and the kitchen sink...literally!

"SANS! WHAT IS GOING ON HERE?!" Papyrus yelled, entering the kitchen. "The kitchen is a mess!"

Sans grabbed his brother's shoulders. "WE'RE OUT OF KETCHUP!" he screamed in horror.

"I DON'T CARE ABOUT KETCHUP!" An angry Papyrus threw his brother off of him. "GO LOOK SOMEWHERE ELSE!"

Sans bolted out of the kitchen without another word.

The skeleton began searching up and down the whole house for his ketchup.

Ketchup was Sans's most favorite treat. He would drink it right out of the bottle.

And he was desperately craving some.

Finally, he went to the last place to check; Frisk's room.

Sans looked under Frisk's bed, her closet, even her laundry basket.

Finally, he looked in her sock drawer and there were several bottles of ketchup!

"My precious!" Sans took the first ketchup bottle and squirtes it's contents right into his mouth.

After consuming the whole bottle, Sans began to realize little Frisk has pulled a prank on him.

Frisk was taking a nap on the couch, unaware of her duncle lurking in the shadows.

"AAAAAAH!" Frisk woke up when she felt her arms and legs restrained. She saw it was Sans's gaster blasters pinning her down.

Sans approached the trapped girl with his hands behind his back. "Well, well, well, so here's my little ketchup thief."

"Sans! I'm sorry! I just thought it would be funny!" Frisk said pleadingly.

"I know." Sans chuckled. "But you still need to be punished..." He wiggled his skinny, bony fingers.

"Oh, no! No! No! No! No!"

But it was too late. Sans started tickling Frisk's stomach. "Cootchie, cootchie, coo! Tickle wickle on your tummy wummy!"

"AHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA! SAHAHAHAHAHAHAHANS, STAHAHAHAP!" Frisk laughed more as the teasing words made the tickling worse. "I CAN'T! I CAN'T!"

"What's wrong? Can't 'ketchup?' he joked.

"NOT FUNNY! AHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!"

Sans tickled her underarms now. "Then why are you laughing? Huh? Huh?"

"STAHAHAHAHAHAHAHAHAHAHAHAHAHAP!" Frisk laughed.

"Tickle, tickle, tickle! Someone needs a good tickle for being a sneaky little thief!" Sans replied, now getting at her neck and sides.

"HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA! EEHEEHEEHEEHEEHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!"

Seeing the red in her face, Sans stopped and called off his gaster blasters. He gently scooped up Frisk and held her like she was his own baby.

"You okay, kiddo?"

Frisk was too busy catching her breath. So Sans decided to help her recover by laying down on the couch, holding Frisk and running her back.

"Snuggle time." Sans sighed as he cuddled up with the human.

Frisk snuggled into Sans's hoodie. The softness made her smile warmly. Frisk was feeling better instantly. She curled up with her duncle and sighed blissfully.

"Sorry if I went overboard." Sans said.

"No, it's okay." Frisk replied. "I deserved it. I'm sorry I pulled that prank on you, Sans."

"Hey, let bygones be gone I always say." Sans said. "Let just rest those tired bones."

Frisk kept smiling. It was a crazy day, but an educational one.

For this little girl learned to never take her duncle's ketchup again. Ever.