Alphys is a scientist in the underground she's the one who created Flowey she also has a Big crush on undyne but she's too scared to tell her you are Frisk

Undyne is one of the Royal guards is has feelings for Alphys but she's scared to tell her she is trying to capture you so she could be a better guard you are Frisk

Asgore is the King of the underground he is the husband of Toriel and the father Of Asriel he is a good King and kind he is trying to protect every monster of the underground you are Frisk

Toriel is the queen of the underground she is the wife of King Asgore she is kind and loving she shaved you before you got killed by Flowey you are Frisk

Asriel is the son of the queen Toriel and King Asgore he is Flowey before he died he is the sibling of chara and he wants to be friends with you you are Frisk

Flowey is Asriel body after Asriel died Flowey is evil and mean but sometimes you can be kind nice but please don't listen to him and don't get in his bad side and you are Frisk

Papyrus is a skeleton he has a brother named Sans papyrus dream is to be in the royal guard he is trying to capture you so he can be in the royal guard you are Frisk

Sans is a skeleton and he has a brother named papyrus Sans loves to make jokes and pranks he is lazy and he loves to eat and drink ketchup you are Frisk

chara is the first fallen human I think they are the sibling of Asriel sometimes they are evil sometimes they are nice and you are Frisk

Frisk is the eight human to fall to the underground they are nice and kind they love to explore the underground please don't be flirting with them and yes you can be any undertale character you want have fun