[A/N: I'm trying a new way to italicize things in the story so if it doesn't work I'll fix it]
Kristen's 'joke' went just about as well as she thought it would. In other words, Sans had no clue until he passed the mirror in the hallway. Then the confusion came and went; after that he was not at all happy.
"kristen come here, please," he said as calmly as he could. The tiny skeleton didn't show, however. Sans sighed in annoyance.
"Kristen. Come here now," Sans said with more authority in his voice than before. Kristen slowly made her way to her father, poorly hiding her grin.
"You know that I like a joke as much as the next person does, but coloring in my entire face isn't exactly funny." Sans said. Kristen saw what was coming next - she'd seen it enough times before. Sans was reaching for the nearest blue marker when Kristen suddenly popped out of the hall.
"Um...Kristen?" Sans asked, all thoughts of redemption forgotten. Suddenly he heard a quiet ting! and his gravity changed, his now blue soul forcing him into the ground. He was now flat-out worried.
"Papyrus...is that you?" Sans asked, a little afraid of the answer. Instead he heard a stream of poorly suppressed giggles. When his gravity - and soul - went back to normal, he saw Kristen, hand over her mouth, corners of her grin showing nonetheless.B
"What did you do," Sans asked sternly. Kristen pointed at the mirror and Sans looked back at it. He didn't see anything...
He started to turn back to Kristen when he saw it. She had gotten him for the repeated other marker pranks by scrawling Your turn to get dunked on! in blue marker...on the back of his head.
"How am I going to get this off?" Sans asked in a mock distressed tone. Kristen burst out laughing on the floor.
"very funny. tibia honest, im not actually sure how you teleported. mind helping me figure it out?" Sans said. Kristen nodded enthusiastically. She loved visiting Alphys at her job at a lab. Sans picked up the still clean child and teleported to Alphys's workspace. The lizard monster jumped at their sudden appearance, but regained her composure soon after.
"H-hi, Sans! And Kristen! ...w-wait. Sans, why do y-you have marker all over y-your face?" Alphys said, looking at Sans's rainbow-colored face in utter confusion. Sans looked at Kristen. Nothing more had to be said.
"Oh. Right. Um...what's t-the visit for?" Alphys asked.
"little miss jokester here teleported. i was wondering if you'd be willing to help us figure it out," Sans replied. To press his statement, Kristen popped outing his arms and onto Alphys's desk.
"Um...okay, j-just give me a moment." Alphys said, then walked into the hall behind Sans. Thankfully, she hadn't noticed Kristen's little redemption message yet. Thank goodness for that.
Alphys returned with a small box/machine thing.
"Kristen, can I put this up to your Soul?" Alphys asked. Kristen nodded, and Alphys did just that.
"Hmm..."
"what?"
"She's got strangely high DT levels for someone her age..."
"will she..."
"I don't think so. It seems they're normal for her. But still, keep an eye on her," Alphys said. Sans nodded, thanked Alphys, and the two skeletons teleported away.