Frisk hear the lines Chara hears when they are found by Asriel when Frisk nearly died after falling into the garbage dump. When you lay in bed enough times and don’t face Toriel at the exit, you get the flashback to those lines again. Every time Frisk is defeated, they hear the very lines Asgore said to Chara as they died, pleading for them to wake up, that they are the future of Humans and Monsters, that they have to stay determined. The second Frisk falls into Undertale, they receive the memories Chara had when they fell in. Chara either intentionally or unintentionally shares their memories every time this happens, every time the soul is broken and Frisk’s and Chara’s essences come together as they come back. Everytime Frisk is defeated, Chara destroys Frisks soul to prevent it being taken, and encourages them to come back to their “save” and return to life with their soul. Chara has only one goal, to grow stronger and feed off Frisks power and determination and soul. Maybe it happens with every human that falls down, maybe it’s only Frisk because only they had a red soul like Chara. From the very second Frisk falls into the world of UnderTale, A bit of Chara’s essence clings to them.
