you we're sleeping in chara's bedroom because.. I don't know.. Plot maybe? Also you've fallen into the underground 2 days ago so good luck with your new life. Chara Is your partner and the only human you see in the underground since the underground was filled with monsters.. You got adopted by Papyrus when you're having a good sleep then someone throws a pillow at your face, it was obviously Chara the lazy prankster

"Wake up sleepyhead"

she started to throw even more pillows to wake you up