You had just left Toriel in the Ruins... As you push open the huge purple door, you're hit in the face with icy cold air and snow. There was nothing but an endless row of trees and a pathway, hopefully leading to somewhere warm..
You gripped onto yourself as you trudged through the thick piles of snow. Each step made you feel heavier, and each gust of wind made you wish you had taken one of the coats from Toriel's closet. Nonetheless, you persevered through the cold.
After what feels like hours, you find yourself at a small, rickety bridge with large... Bars? Whatever.
Right as you go to step onto it, you freeze as you hear loud, echoing footsteps. You stay frozen in place as they slowly get closer and closer to you... Before you know it, whatever is behind you comes to a stop, mere inches behind you.
"Human." A deep, cold, and slow voice speaks to you. "Don't you know how to greet a new pal?" "Turn around and shake my hand."
Your brain practically went on autopilot as you turned around to a shadowy figure. It seemed to stare at you for a moment before holding out it's hand. With a bit of hesitation, you reached out and interlocked your fingers, but before you knew it, a loud farting sound rang throughout the forest...
It was almost as if the shadow disappeared, and you could witness who was speaking to you... A skeleton.
"Hehehe... The old whoopy coushion in the hand trick. It's ALWAYS funny. Anyways, you're a human, right? That's hilarious." He looked down at you, an amused smile appearing on his skull. "I'm Sans. Sans the Skeleton."