Sans:

You were smoking your pipe on the couch as Sans walked in, he looked annoyed like always. "(Y/n). I, the terrible Sans, order you to STOP smoking." You chuckled and kept puffing the tobacco in the pipe, Sans growled as he walked over. When he missed from slapping your neck, you giggled at the light brush of his glove. "M-m'lord! D..don't do that!" You said through some small giggles, Sans smirked with an evil look, sending your magic blood running cold. Sans tackled you down, making you drop your pipe and the tobacco spreading on the rug. Sans held your arms over your head as you sweated nervously.

"I will make you squeal and stop smoking." Sans growled playfully, you flinched as he lowered his skull towards your neck. "D..DONT!" Sans ignored your plead and blew a raspberry into your neck, you squealed as Sans moved his hands towards your ribcage. You had your hands on his shoulders as red-orange tears left your eye sockets. "SHAHAHAHANS! PLEAHAHAHASE! I CAHAHANT HAHAHAHAHANDLE IHIHIHIHIT!" You begged, Sans smirked in the raspberries before he lifted his skull. "Hmmm... what if I were to tickle you... here?" You shrieked as he tickled your ribcage.

"NAHAHAHAHAHAHAT THERE! PLEHEHEHEAHAHAHASE! SAHAHAHAHAHAHAHAHAHANS! AHAHAHAHAHAHA! PLEHEHEHEAHAHAHAHASEHEHEHE! STAHAHAP! I'LL STHAHAHAHAP SMOKING SO MHAHAHAHACH!" Sans smiled as you stopped struggling and just allowed him to tickle you, you seemed to be enjoying being tickled, it made Sans feel like the big brother he should be towards you. 'I should do this to them more often...' Sans thought as he stopped tickling you. You were panting with a red-orange blush and tears on your face before Sans gently rubbed your hipbones, calming you down a little (no sinning. *throws sinners out of window*). "I might tickle you again... I think I like your laugh..." "O..Ok S...Sa..Sans.." Sans saw you were so tired to correct yourself. He chuckled and carried you into your room so you could rest.

Papyrus (Technically he knows your ticklish):

You were in the kitchen, trying to find Papyrus's barbecue. You heard it was tangy yet sweet at the same time. You usually drank ranch but, you wanted to try some. "Where is it? Where- Oh!" You whispered as you saw the bottle in a cabinet. Before you could reach for it, your soul turned orange and you were now floating in front of Papyrus. "What are you doing?" Papyrus asked, you looked away from him and replied "N..nothing!" Papyrus rose a curious eyebrow and smirked. "Sooo... why were you trying to steal my barbecue?" Papyrus asked, making you float to the couch as he walked over.

"I... I wanted to try some..." You answered, suddenly Papyrus pinned you down while he sat on your legs. "Now, if you asked, I would let you buuuut... You didn't sooo..." You started to giggle as Papyrus tickled your spine. "I'm gonna have a great time!~" Papyrus teased, you started to giggle more as he tickled up your spin. "Pahahahahahahapy! Nuuuu! I'm sahahaharry!" Papyrus smirked, he remember when you were a baby bones that your mom always tickled your ribcage, it was your most sensitive spot. "Hmmm... I want to see if ma was right about... this!" You squealed as Papyrus tickled your ribcage.

"PAHAHAHAHAHAHAPY! NUUUUU! I'M SAHAHAHAHAHARRY! AHAHAHAHAHAHAHAHAHAHA!" You tried to squirm free out of Papyrus' ticking hands. Sadly, it failed. Now, Sans WOULD be able to save you if he was home. But, he was off training. You were on your own. Papyrus suddenly got an idea and started to pull up your shirt and hoodie. "DONT YOU DHAHAHAHAHAHAHAHAHARE! HAHAHAHAHAHAHA IHIHIHIHIHIHIHI NUUU! STHAHAHAHAP!" You shrieked as Papyrus blew a raspberry into your ribcage. "Awww... is the wittle baby bone a wittle ticklwish?" Papyrus teased before blowing another raspberry, you screamed in laughter and tried to push Papyrus' skull away. "WHAT IS GOING ON HERE?!" Papyrus turned around as Sans stood there, angry and confused. "Oh. M'Lord. I was just punishing (y/n) for trying to steal my barbecue." Papyrus explained, you sat up and pulled your shirt and hoodie down. Sans rose a curious eyebrow while sending you an evil smirk. "I'M OUT!" You squeaked, teleporting. "Find her." Sans ordered with a playful tone, Papyrus snickered and teleported.