Susie is rude, sarcastic, and not afraid to speak her mind. She is outspoken, selfish, and rebellious, tending to protest or favor her own interests. At times, she threatens with physical violence, rarely as a joke. However, Susie is alot more gentle and mindful to those who are kind to her. With friends, she is expressive, willing to talk about herself, and considerate of their opinions. Susie enjoys the company of her friends, and teases them often. She is observant of her friends emotions. Susie tries to comfort her friends, but she tries to avoid stressful topics. Susie is quite vulgar and usually informal. She also falls asleep easily, and is quite gluttonous when it comes to her friends cooking.

Kris is quiet and introverted. Their reticence causes their friends to be more observant of their body language to gauge reactions. Kris does not speak often, and is described as having a "deadpan, mumbly voice".Kris is not normally energetic. They have a history of not waking up on time, and often sleep through the start of class. Kris also prefers someone else getting them to and from school. After Kris's brother, Asriel, left for college, they grew distant from their few friends in the intervening time before the events of Deltarune. Kris's side of their and Asriel's shared bedroom is strikingly bare; the shared game console rests underneath Asriel's bed, their old children's books are stored in Toriel's classroom, and there is nothing on their shelves. It is implied that Kris enjoys thinking back on their childhood, and that they are unsettled by the thought of growing up. Kris is non-binary, and goes exclusively by the singular "They" pronoun. Kris is also quite mischievous, and a bit of a prankster.

Noelle is friendly and cheerful, often seen smiling and laughing with a "fahaha". She is considerate, helping Alphys retrieve chalk and Berdly and Kris with studying and homework. Her speech mannerisms are very polite in the Japanese localization. Noelle is also very timid, easily flustered, unassertive, and sometimes has trouble voicing her thoughts. She apologizes often, and stays quiet about her feelings, such as her crush on Susie or her frustration with Berdly. Her father describes her as "defenseless" and scared of everything, including horror movies, bugs, and She likes feeling scared since she associates fear with being comforted.[9][10] This is likely the reason why she seems attracted to the idea of Susie bullying her.