Main
- Robot Jones (voiced by Macintalk Junior in season one and Bobby Block in season two) is a robot who does whatever he can to fit in the human society, which can sometimes go awry. Whenever the day ends he adds to his memory called Data Log Entry something he learns through the experience. His brain is a giant light bulb. Macintalk Junior was replaced by Bobby Block to prevent a lawsuit from the Apple company. Moreover, Block's voice was also used to dub over the season one episodes.
- Dad Unit is Robot's father. When he says something, he often says it three times; one example would be "Listen to your mother! Listen to your mother! Listen to your mother!" as said in the inaugural episode. He has one hand, wears a tie and in his focus on tasks he often gets into shenanigans such as smashing through walls. He is voiced by Macintalk's 'Ralph' voice, which was also used for the voice of Auto in WALL-E.
- Mom Unit (voiced by Grey DeLisle) is Robot's mother. She is pink in color and her hands look like the ends of a gas pump's hose which she uses for giving fuel to her fellow units. She seems to generally have a no-nonsense attitude.
- Socks (voiced by Kyle Sullivan) is the best friend of Robot Jones. He is quite a fanatic to rock music. He has blond curly hair and wears a green jacket.
- Cubey (voiced by Myles Jeffery) is the shorter friend with dark, straight hair, sunglasses with window blinds for lenses, and roller skates. He is a video game lover.
- Mitch (voiced by Gary LeRoi Gray) is a lad often seen wearing headphones, a red sweater and sandals. His eyes are obscured by his long hair. In "Scantron Love", his last name was Davis.
Recurring
- The Yogmans (voiced by Josh Peck and Austin Stout respectively) are the notorious young genius twins of the show. They wear red hats that resembles the 1980s band Devo's energy dome hats, yellow shirts, and black sneakers. Lenny is tall while Denny is short. They do whatever they can to take Robot's brain.
- Shannon (voiced by Grey DeLisle) is a girl whom Robot loves because she has more mechanical attachments than any human he has ever seen, specifically a large orthodontic appliance and a prosthetic leg. She is unaware that Robot has a crush on her and typically finds him more of an annoyance than anything else. Shannon talks with a lisp.
- Mr. McMcMc (voiced by Maurice LaMarchie in the pilot and Rip Taylor in the series) is Robot Jones' math teacher.
- Clancy Q. Sleepyjeans (voiced by David Koechner) is the school janitor.
- Mr. Workout (voiced by Dee Bradley Baker) is the Gym teacher in Polyneux Middle School. He forced Robot to take a shower in "P. U. to P. E.".
- Ms. Rucoat (voiced by Grey DeLisle) the English Teacher.
- Ms. Kavendash
- Principal Madman (voiced by Maurice LaMarche in the pilot and Jeff Glen Bennet in the series) is the principal of Polyneux Middle School. His mustache resembles that of Adolf Hitler's; as such, he is very tyrannical to his students.
- James Nob (voiced by Gedde Watanabe) is the tyrant owner of Nob's Arkaid, where Robot and his friends hang out. He keeps telling kids that they're breaking his arcade machines, every time they play with them. In "Hookie 101", it is revealed that his arcade gives a discount on game tokens during school hours.
- Gramps Unit (voiced by Macintalk's 'Zarvox') is Robot Jones' grandfather. Gramps Unit sounds like Robot Jones' father, but he could be the dad of either Dad Unit or Mom Unit