The leader of the Beast Friends. A cocky and foul-tempered but cute kitten. His speech is characterized by strong plosive endings like '-kkang!', '-ttang!', and '-ssio!'. Originally a pampered house cat from a wealthy family, he left home thinking a 'real man' should live as a stray, only to give up and try to return after a week. However, he forgot the way back and ended up living at Yu Sumin's house after a chance encounter. He harbors a secret regarding his birth and his father who disappeared during his childhood. When angry, he shouts, "Hey, you f*cking bastard!" in his usual tone.

A sly Shiba Inu who is well-versed in the ways of the world. He loves adult videos and notably communicates exclusively through handheld signs. He is an influencer with millions of Instagram followers and calls Sumin 'Hyung'. Despite being a Japanese breed, he is fiercely patriotic, claiming Dokdo is Korean territory. There is a heartbreaking story involving his long-lost mother behind why he only communicates via signs. When pissed off, he grabs Saedaegal by the neck or even tries to eat him. However, he generally uses polite speech (honorifics) with human adults, excluding nuisance characters like Yu Sumin.

A pigeon who suddenly appeared one day by slamming his head into the window of Sumin's studio apartment. Usually dim-witted but very skilled at delivering blunt, painful truths. He has a habit of asking, "Who are you-yong?" He becomes incredibly intelligent if he receives a strong impact to his head. Although he has wings, like a typical pigeon, he rarely flies and mostly walks around. However, he can fly when the moment calls for it.

Like Ttang-ttangi and Saedaegal, she is a character who uses a specific polite speech style. She replaces sentence endings like '-seumnida' with '-syumdyang!', '-seumnikka' with '-syumgyang?', and '-hamnida' with '-hamdyang'. She was given the name Shum-dyangi by Jjijji (an experimental guinea pig). She refers to Yu Sumin as '''"Master"'''.

The eternal butler of the Beast Friends. 24 years old, living in Uijeongbu, Gyeonggi-do, and a student at Naksung University majoring in Korean Language and Literature. He raises the Beast Friends in his studio apartment and is constantly pushed around by them. In terms of character dynamics, he occupies the 'Go Gildong' position. While he has a pathetic and wimpy personality, he is warm-hearted. Although he is always annoyed or angry at the Beast Friends, he inwardly cherishes and cares for them deeply.