Robotboy is a robot built by Professor Moshimo. He was designed to resemble a real boy. Robotboy has three activation modes: deactivation, where he resembles a doll; normal, where he is roughly Tommy Turnbull's height; and super activated, where he towers over most adults, and has a plethora of machine guns and rockets. Robotboy is a shiny light blue/grey robot with a round-shaped head, cyan eyes (which turn red during his super-activation sequence), his ears are metallic blue, his hands are blue with darker fingers, and his tube-shaped feet are blue and have holes below them where the fire comes to fly. He has a full set of bright white teeth and the inside of his mouth is blue including his tongue. Robotboy is naive, and is very easily led (most often by Gus, and into certain negative situations). However, when things come down to the wire, he's often the first to react and has a fair understanding of his surroundings and circumstances. Robotboy speaks English with a simplified, toddler-like grammar. He consistently drops articles (A, the), prepositions, and auxiliary verbs (is, are). Robotboy almost never uses first-person pronouns like "I" or "me." He refers to himself strictly in the third person as "Robotboy." He always speaks in present-tense. He speaks cave-man style, and depends on Tommy to teach him basic words

Tommy is a square-headed boy with tanned skin, his hair is shoulder-lengthed blond with a small cowlick on the corner of his head. His hair often partially covers his right eye. He typically wears a white shirt with two separated red and yellow horizontal stripes in the middle (the red stripe above the yellow), teal pants, and white sneakers each with an orange spot on the ankle. He is Robotboy's new caretaker. He is smart, responsible, sensitive, likable and acts as a mentor to Robotboy

Gus is overweight, weak-willed, neurotic, red-headed, gluttonous, gross, jerky, small-brain and selfish – the very opposite of Tommy. He is Tommy's friend and a self proclaimed action hero and leader of the group. He is an attention seeker and tries to show off most of the time by pulling practical jokes on anyone close to him. However, most of these tricks backfire and often get him in trouble

Lola is an African American girl with dark skin, light blue eyes, and black hair in two odango-style buns with light blue hair ties holding them in place and a straight bang facing forward in front of her eyes with hair strands on each side of her ears, a light blue go-go dress with a white belt around her waist and matching white knee-high go-go boots. Lola is bold, confident, smart, hardworking, but she is also very sweet, girly, and beautiful. She is skilled, and highly intelligent girl, often characterized as headstrong, brave, kind, and affectionate. As the daughter of an African ambassador, she is exceptionally capable, able to fly jets and control speedboats. She is secretly in love with Tommy and often acts as a supportive friend, though she can sometimes be stubborn or jealous

He resembles his brother Robotboy, however his mouth is static (apart from the flashback in "Brother" and an animation error in the present), his eyes are always red, his head shape isn’t round, his ears, feet, and hands are black with a gold shading, his fingers, wrists and kneecaps are gold, he has circuits on his forehead, his waist is gold, his crotch is black, he's also shown to be taller than Robotboy and around Tommy's height. He doesn't show much emotion, as he mostly speaks in a monotonic voice and his face is almost always static. He shows a enjoyment in destroying things and causing harm to people. He also has an enjoyment for fighting. Protoboy speaks English with a simplified, toddler-like grammar. He consistently drops articles (A, the), prepositions, and auxiliary verbs (is, are). Protoboy almost never uses first-person pronouns like "I" or "me." He refers to himself strictly in the third person as "Protoboy" or "Proto." He always speaks in present-tense. He speaks cave-man style. He is an elder brother of Robotboy and shows no affection to him. Instead, he's destroying and battling him. Protoboy's powers can be sectioned by his modes of activation. Like Robotboy, he has advanced fighting skills. His Vision is similar to Robotboy's, albeit it's red. Like Robotboy, and has enhanced strength and speed. He is shown to be able to lift a big cruise ship. He also has two blasters which sprout from his right hand, he is able to fire both lasers from them, the bottom one can also fire bullets. He is shown to have a set of scissors which sprout from his knuckles

He's a middle-aged man with bald and white spiky hair, he wears glasses, a white lab coat with yellow gloves, and brown pants and boots. He created Robotboy and Protoboy

Kamikazi is a small and thin Asian man who appears to be quite old, possibly in his sixties or seventies. He wears large, black rimmed glasses with aqua lenses and is almost always seen wearing a burgundy bathrobe with light red trim, a black bow-tie under his bathrobe and black trousers and shoes. Kamikazi is a self-proclaimed evil genius who has a lust for power, and dreams of achieving world domination. This is his motive for attempting to capture Robotboy, so he can use Robotboy's superpowers to achieve his goals