So, this is a bit late, but WHATEVER!!!

So! You were invited to a party with the underground crew!!

Toriel- Witch
Sans- Skeleton Key
Papyrus- Mummy
Asgore- Frankenstein
Undyne- Piranha
Alphys- Kawaii Anime Girl
Mettaton- Vampire
Napstablook- Ghost
Frisk- Jason

If you want Laney!
Laney- Fallen Angel
Goldie- Cupid
Dark- SATAN