You were walking in a dark forest after having passed a door in Toriel's house just after having killed her

You begin to hear footsteps heading towards you

Human. Don't you know how to greet a new pal? Turn around and shake my hand

You turn around slowly and shake the stranger's hand

Suddenly a fart sound was heard, it was a Sans Joke

Heheh…it's ALWAYS funny. Anyways, you're a human right? That's hilarious

Sans said laughing