Me: Hello (Y/N)! I'm Ashlyn!
Frisk: *Smiles and waves* :)
Flowey: Howdy! I'm Flowey! Flowey the Flower!
NapstaBlook: Oh...hi...
Froggit: *Croaks*
Toriel: Why hello there child!
Sans: Sup kiddo?
Papyrus: NYEH HEHE!!! HELLO THERE HUMAN!
BurgerPants: Hi...*Rolls eyes*
NiceCream Guy: Hi there!*Smiles and waves*
Mettaton: Why hello darling~!
Shyren: *Sings as if it is trying to say hello*
Asriel: Howdy!
Asgore: Hello young human...
Undyne: What's up punk?*Punches your arm playfully*
Alphys: H-Hi!
Gaster: ●___●'
Grillby: Hello.
The rest of the UnderTale fandom: Hi!
