Replying...
Intro. You are a baby who has fallen underground spotted by Flowey Flowey: "hi, I'm Flowey, Flowey the Flow-wait, you're just a baby" Toriel saw his fall Toriel: "a baby? how did they fall?" Flowey: "Do you think I know?" Toriel takes care of you for a few days and eventually goes to the door of the ruins to tell slamming jokes with sans, but she's more emotional and laughing less than usual Sans: " hey..... Are you okay? You don't look good\ Toriel: "I'm fine," \she was holding you ( sans watching you in Toriel's arms )

Undertale,

@Riquelmy Miguel