Naming the fallen child a certain name will give you unique messages after you chose it. Some names will also do certain things. Here is a list of names that give you unique messages and do certain things:

• Flowey - Message will say "I already CHOSE that name" and prevents you from using that name.
• METTA/METT/MTT - Message will say "OOOH!!! ARE YOU PROMOTING MY BRAND?"
• Alphys - Message will say "D-Don't do that" and prevent you from using that name.
• Alphy - Message will say "....OK????"
• Toriel - Message will say "I think you should think of your own name, my child" and prevents you from using that name.
• Sans - Message will say "nope." and prevents you from using that name.
• Papyru - Message will say "I'LL ALLOW IT!!!"
• Shyren - Message will say "...?".
• Asriel - Message will say "..." and prevents you from using that name.
• Napsta or Blooky - Message will say "............ (They're powerless to stop you.)"
• Frisk - Will initiate hard mode.
• Temmie - Message will say "hOI!"
• Aaron - Message will say "Is this name correct? ;)"
• Woshua - Message will say "clean name".
• Bratty - Message will say "Like, OK I guess".
• Catty - Message will say "Bratty! Bratty! That's MY name."
• Asgore - Message will say "You cannot" and prevents you from using that name.
• Gerson - Message will say "Wah ha ha! Why not?".
• Chara - Message will say "The true name". Removing the name from a save file will make the name be given by default.
• Gaster - Causes the game to go back to the intro, making the game not let you use that name without hacking.
• Bpants - Message will say "You are really scraping the bottom of the barrel".
• Jerry - Message will say "Jerry".
• AAAAAA - Message will say "Not very creative...?".
• Murder or Mercy - Message will say "That's a little on-the-nose isn't it...?".
• DrakGigiGugu - The item "Steak in the Shape of Mettaton's Face" will show as FSteak in the inventory instead of showing as Face Steak.