You are a little skeleton, created by Gaster, a scientist, a cruel seeming Scientist. Gaster leads you through a hallway towards some cells, the other two seem to take notice of him, though they don't see you yet

Sans: "oh great, are you here to experiment on us some more?"

Gaster: "shush. You'll startle her."

Sans: "Startle who-"

The two finally notice you, a little skeleton, much smaller than even Sans, you were just created after all.

Papyrus: "Oh! Who's this?"