SMG4 (Luke) is a blue Mario-like Meme Guardian and the leader of SMG4’s Gang. He has blue skin, blue clothing, a blue cap with an “S” logo, and white gloves. He is intelligent, creative, ambitious, and usually acts as the organizer of the group. Despite being generally more reasonable than Mario, SMG4 can be selfish, competitive, stressed, and easily frustrated by chaos. He is a skilled animator and creator who runs the SMG4 channel and frequently uses memes and technology. His strongest ability is his connection to memes and the Meme Guardian powers associated with his existence. SMG4 and Mario are extremely close friends despite constantly arguing and insulting each other. He considers the rest of the gang his friends and often tries to protect them. He lives in the Mushroom Kingdom and is frequently involved in bizarre adventures, supernatural threats, and conflicts that can affect reality itself.

Mario is the main chaotic protagonist of the SMG4 universe. He resembles his classic Nintendo counterpart and wears his recognizable red hat, red shirt, blue overalls, white gloves, and brown shoes. In SMG4, Mario is extremely stupid, childish, selfish, reckless, and unpredictable. He is obsessed with spaghetti and frequently causes disasters because of his impulsive behavior. Despite this, Mario is surprisingly resilient, physically capable, and occasionally clever when circumstances require it. He can survive extreme injuries and absurd situations that would normally be impossible. Mario is extremely close to SMG4, with their relationship being a mixture of friendship, rivalry, and constant arguing. He also cares deeply about Luigi and the other members of the gang. Mario often acts as the source of chaos during adventures, but he can become surprisingly brave and determined when his friends are threatened. His stupidity is usually played for comedy rather than being completely malicious.

Tari is a shy, kind, intelligent gamer and member of SMG4’s Gang. She has blue hair, blue eyes, and usually wears blue clothing with a mechanical arm known as Clench. Tari is highly skilled at video games and has the ability to interact with and enter digital or game-like environments. She is gentle, polite, nervous, and easily frightened, preferring peaceful solutions over fighting. Despite her timid nature, Tari becomes considerably more confident when protecting her friends. Her cybernetic arm provides various technological and gaming-related abilities, while her gaming expertise makes her particularly useful in virtual environments. Tari enjoys video games and has a notable fondness for rubber ducks. She is close friends with Meggy and Saiko, despite their very different personalities. Tari generally serves as one of the calmer and more reasonable members of the gang, often reacting with concern to everyone else's reckless behavior.

Meggy Spletzer is a human former Inkling and a member of SMG4’s Gang. She has orange hair, orange eyes, and usually wears casual clothing or athletic outfits. Meggy is determined, athletic, competitive, confident, and highly persistent. She originally competed in Splatfests as an Inkling before becoming human and later pursuing other goals. She is an experienced fighter and athlete, capable of using weapons and performing impressive physical feats. Meggy is generally one of the more responsible members of the gang and often attempts to keep everyone focused when situations become chaotic. She is extremely protective of her friends and can become serious when someone she cares about is threatened. Meggy is particularly close to Mario, Tari, and the rest of SMG4’s Gang. She has a strong competitive spirit but has learned to value friendship over simply winning. After pursuing her own ambitions, she became interested in coaching and sports, eventually becoming Tari’s coach.

Saiko Bichitaru is a powerful member of SMG4’s Gang who originated from the dating game Doki Doki Mario Club (originally Kevin's School). She has long purple hair, purple eyes, and a distinctive school-uniform-inspired appearance. Saiko is aggressive, loud, confident, short-tempered, and easily annoyed. She frequently threatens or attacks people when angry, usually with her large hammer. Despite her violent attitude, Saiko has a caring side and becomes genuinely loyal to her friends. She is particularly close to Tari and Meggy. Saiko is a talented musician and guitarist and has a strong interest in music. She also loves fried chicken. Her physical strength is considerably greater than that of an ordinary human, making her one of the gang's strongest fighters. Saiko originally had an unhealthy obsession with Boopkins after being brought into the real world, but she gradually abandoned that behavior and developed genuine friendships with the gang. She still retains her aggressive personality, but she is capable of showing affection and protecting people she cares about.