The rules are rules and unfortunately they can't be broken.
"Uhh...Alphys...What is that..?" Frisk asked confused as Alphys was showing her a weird plant. It looked to have little white fruits on it then it hit you.
"NOOOOO!" Frisk said backing away and shaking her arms desperately.
"B-but Frisk-chan!" Frisk scurnched up her nose as the tiny lizard was making puppy eyes.
"ugghhh...fine...what's the plan..?" Alphys beamed.
"t-to get m-me and Undyne-Senpai underneath at the same time...J-just bring her here!" Frisk frowned.
"Isn't it that plant that if you're underneath you need the person you're underneath with..?" Alphys smiled.
"Y-yes! I..i just w-want to do this..p-please. It's a h-human t-tradition!" Frisk looked at it then felt a familiar hand on her shoulder. She still jumped up in surprise. The culprit smiled.
"sorry frisky. wassup?" Frisk pointed at the mistletoe. Frisk then made a chopping sign on her neck. Sans raised a bone-brow.
"anddd that is..?" Frisk sighed and face-palmed.
"It's mistletoe." Sans immediately blushed light blue.
"w-woah there! what are you doing with..THAT??" Alphys then explained to Sans her plan of getting Undyne underneath the mistletoe with her.
"Help me up so i can hang this..?" Sans sighed.
"alrighty then." He used his blue magic and Frisk hanged the little plant.
"O-ok! W-when you f-finally get to Undyne and get h-her here...c-contact me!" Frisk looked dumbfound.
"Hold up...YOU are leaving..?" Frisk said. Sans frowned as well.
"why are you leaving when you want to be the one kissed..?" Alphys looked down.
"t-to prepare myself.." Frisk sighed and looked behind her.
"Sans...you coming with..?" Frisk asked as they looked at the road taking to the training patch where Papyrus and Undyne were at.
"sure, i guess." They walked to her and smiled.
"yo! Undyneeee!" Frisk said. The fish monster turned to her and norrowed her eyes as she took her eye-patch off.
"yeaahh...why are you speaking like that..?" Undyne asked. Frisk shrugged.
"Just Alphys wants to see you in 30 minutes in the garden." Undyne's eyes widened.
"You serious?! ALPH?! Oh god! Ok ok ok !! I'll be there in 30! Sorry Papyrus i gotta go!" Papyrus frowned then gave a thumbs up to the fish monster. Frisk looked at Papyrus who smiled.
"SOOO WHAT'S HAPPENING?" Frisk explained the plan to Papyrus as the three walked back. Sans, Papyrus and Frisk then hid in the bushes and found out something...a lot of people walked in the garden. Frisk and Sans had to always try to get them to take another road or to let only one person cross at a time. It was quite exhausting. It has been 45 minutes since they had been struggling with this and there was still no sign of either of the two. That's when Sans thought of something. He thought of the night when Gorgette attacked his pun-buddy AND Frisk too. With magic! That's when an idea came to his skull.
"heyyyy~~ friskyyy~~" Frisk norrowed her eyes.
"nooo..you want something, i know it!" Sans smirked.
"let's pull a prank on little sneeky-snakes." Frisk raised a brow.
"Listening..." Sans smirked.
"sooo~ what if we get her here to think asgore wants to see her...and it's actually alphys and undyne kissing under the mistletoe and TECHNICALLY asgore isn't even in the castle at this hour." Frisk frowned then shook her head.
"what..? no..?" Frisk smirked.
"not evil enough..get Asgore and Toriel here." Sans sockets widened and his smile stretched.
"you are pure evil you brilliant human!" Now it was time for the plan. First they went to Toriel.
"Oh! You guys want all of us to play in the garden..? Sure!" Frisk smirked then Sans and Papyrus went their separate ways from her. Sans and Papyrus managed to convince Asgore fast. You..? You just made Gorgette mad so she had to chase you. Frisk was running when she noticed that Toriel still didn't get there. Damn it! She was too into her reading and she actually brought Gorgette to the mistletoe. Alphys and Undyne were also coming and Gorgette stopped dead in her tracks when she saw Asgore.
"GOREY~~!!" The monster exclaimed and Asgore backed away a bit. The snake monster pushedFrisk to the ground and made her way to the prince. That's when MK came into view and was coming for Frisk to help her. Sans sockets widened when they both noticed the mistletoe above Frisk. He teleported in front of her and helped her on her feet. Alphys squealed.
"YOU T-TWO ARE UNDERNEATH!!" Sans and Frisk looked up. Frisk and Sans both flushed. Oh god....
"W-wait! THIS WAS YOUR IDEA THOUGH!!" Frisk said to Alphys. Alphys pushed her glasses on her muzzle and smirked like some badass anime character. Undyne roared with laughter.
"NO WAYYY!! KISS HER! KISS HER! KISS HER!!" Undyne chanted. Toriel came into view and looked at the two of them who underneath the plant. She started giggling and giving Frisk thumbs up. NO! Sans sockets were blank as people were chanting 'Kiss her'. That's when Mk stepped in.
"If you won't I WILL GLADLY WILL!" Sans eye-lights came back as he looked at the armless lizard monster.
"OH HO HO! no you don't!!" He bent Frisk backwards and kissed her. Undyne's mouth fell agap as Alphys squealed. Asgore started laughing and Toriel covered her mouth saying 'Oh my~'. Frisk's eyes were wide. But then she closed them and when the two departed she squeeked. They both were now red, respectivly blue. Alphys then got Undyne under the mistletoe and the two kissed as well. Gorgette tried to bribe the price underneath the plant but he was already trying to get Toriel underneath. Mk left with his tail between his legs as he saw he missed his chance. Papyrus was trying to cheer him up, even if he didn't understand what was wrong. Frisk and Sans were just sitting in the grass looking at them. They looked at each other and he said.
"never speak of this..?"
"Never speak of this." They both made the little handshake they had for this type of things. Their pinkies would make a pinky promise before pertending to pull a zipper on their mouth, lock it and throw the key. Sans then looked at Frisk and smirked.
"wanna push Toriel and Asgore under the mistletoe..?"
"ABSO-FREAKING-LUTELY!" And the two smiled at each other as they got up and were going to perform their evil deeds.