Main •
Rusty (voiced by
Pamela Adlon) – Quark Industries's intended replacement for the Big Guy, a
robot with real
artificial intelligence and powered by nucleoprotons. However, Rusty is far too inexperienced to face the threats that the Big Guy normally handles, so he is relegated to being Big Guy's
sidekick and trainee. He idolizes Big Guy, but is unaware that his hero is actually a human inside a metal suit. He has a very childish and toylike look, including his size which makes him physically unimpressive. He is in fact very powerful and impervious to most damage. His behavior also resembles that of a human child, quite immature with strong emotional reactions. •
Big Guy (voiced by Jonathan David Cook) – Designated as the BGY-11, the so-called "robot" champion of Earth is actually a heavily armed
battle suit, piloted by Lieutenant Dwayne Hunter. When Quark Industries failed to produce an actual robot with artificial intelligence, the solution was to use a human pilot. Big Guy appears to be roughly tall (when seen interacting with the environment, notably people), is able to fly thanks to rocket boots, possesses great strength and resilience, and is armed with a variety of integrated weaponry. •
Lieutenant Dwayne Hunter (voiced by
Jim Hanks) – The Big Guy's pilot, a secret known only to a few, otherwise known as Big Guy's chief mechanic to those not in the know. He has a crush on Dr. Slate. While in Big Guy, Hunter typically will say "for the love of Mike" when exasperated, making it Big Guy's catchphrase per episode. •
Dr. Erika Slate (voiced by
Gabrielle Carteris) – A scientist at Quark Industries, she developed Rusty's human emotional grid and acts like a mother to Rusty. She is one of the few who knows the Big Guy's secret, discovering it by accident when Rusty was looking for a Big Guy fansite and accidentally hacked into confidential files on Big Guy's creation. •
Dr. Axel Donovan (voiced by
Stephen Root) – The President of Quark Industries, a robotics firm. He is a caricature of capitalistic greed and moral cowardice. •
Pierre Donovan (voiced by
Mary Kay Bergman) – The nephew of Dr. Donovan, a teenager physical copycat of his uncle, quite arrogant and manipulative but may have some technical skills related to robotics. •
R-G-B Robots (voiced by
Maurice LaMarche in "Birthday Bash",
Kevin Michael Richardson in "The Big Boy",
Dee Bradley Baker in "Rumble in the Jungle") – A trio of red, green, and blue robots that work for Dr. Donovan. Due to a corrupt code in their system, they fail at following the simplest of commands which ends with them getting wrecked. These robots are regularly destroyed and rebuilt without being improved. •
Jenny the Monkey (voiced by
Kathy Kinney) – A monkey who talks and usually sits on Dr. Donovan's shoulder while making fun of Quark's scientists and employees. She has a keen sense of self-preservation. •
Jo, Mack, and Garth (voiced by
Pamela Adlon,
M. Emmet Walsh, and
Kevin Michael Richardson, respectively) – The Big Guy's pit crew and Dwayne's Hunter's friends. They serve on the
aircraft carrier S.S. Dark Horse, which acts as Big Guy's base and stores his
airship. •
General Thornton (voiced by
R. Lee Ermey) – A United States Army general who heads the government's BGY-11 Commission that created the Big Guy. He helps keep the Big Guy's secret from Rusty and the others.
Villains •
The Squillacci Empire – The very first villains seen in the series, they are squid-like tentacled aliens who make
crop circles, attempt to
experiment on cows and other stereotypical alien actions. Their attempts to conquer the Earth have been repeatedly thwarted by the Big Guy. It is later revealed that, if not for the Big Guy, the Squillacci Empire would have ruled the earth. •
Legion Ex Machina – An enigmatic group of six advanced robots who aim to destroy humanity and create a robot-heaven of "Robotopia". Though not meant for combat, they proved to be surprisingly strong, resilient and agile, far more than an ordinary human being. The series ends on a
cliffhanger, where it is discovered that there is a seventh Legion Ex Machina that Big Guy and Rusty have yet to defeat. •
Legion Ex Machina #1 (voiced by
Clancy Brown) – The de facto leader of the group. He was the first of the legion to come online and can create complex tactics very quickly. In the episode "Double Time", Legion Ex Machina #1 is killed after being thrown against and disintegrated by a powerful force field. He is the sixth and the last member to be destroyed. •
Legion Ex Machina #2 and #3 (both voiced by Clancy Brown) – Since they both lacked emotions they are nearly identical other than their looks. They often disagree on things and are often at each other's throats at times. However they are completely loyal to Legion Ex Machina #1 and would respect #1, although they are always seen as equals. In the episode "Double Time", Legion Ex Machina #2 is destroyed by Rusty, who drags him into the blades of a gigantic fan and tears him to pieces. Legion Ex Machina #3 is later destroyed when Big Guy pushes him into an acid-filled cauldron. •
Legion Ex Machina #4 (voiced by Clancy Brown) – He fights Big Guy and Rusty in the first time in "Little Boy Robot Lost", and is presumed destroyed but later is revealed still active in "The Bicameral Mind". In the episode "Donovan's Brainiac", #4's brain is removed by Pierre Donovan and placed in the body of a toy robot. He attempts to destroy the surrounding area by causing a nuclear meltdown, but is thwarted and destroyed by Big Guy. •
Legion Ex Machina #5 (voiced by Clancy Brown) – The first Legion member to meet the Big Guy. He takes over a munitions factory when meeting with the Chopshoppers, but is thwarted when Big Guy throws him into liquid nitrogen, freezing him solid. Rusty then shatters #5's frozen body, destroying him. •
Legion Ex Machina #6 (voiced by
Dean Haglund) – Also known as Dr. Gilder, #6 was the only member whose emotion grid was fully intact. However his emotions are highly exaggerated and are considered by his peers as a weakness. #6 is initially portrayed as a shy, weak if a bit disturbed scientist but was soon revealed as a Legion Ex Machina member. His emotions also changed to a sadistic and psychopathic killer. #6 is killed by Big Guy, who drops his body into a grinder. • '''The Legion's creations''' – The creations of the Legion that fight Big Guy and Rusty. •
Argos – Two robots created by the Legion. The first – roughly the size of Big Guy with similar armament – is destroyed by Big Guy and Rusty. The second Argos is much larger, roughly the size of a skyscraper, but not meant for destruction. Argos is destroyed after its Vortex Cannon is turned against it. •
The Eliminator – A heavily armed Quark Industries robot that #6 hijacked in an effort to eliminate Donovan in revenge for the destruction of various robots he had created for Quark. It is subsequently defeated by Big Guy and the control drone implanted by Gilder discovered. •
Project Nova – A large three-legged robot armed with a powerful energy cannon; it was apparently designed and its development intended to be overseen by #4. However, during a mission to acquire fuel for its cannon, an attempt by Rusty to download information from the Legion's systems resulted in him and #4 switching programming. As a result, Rusty creates his own version of Nova, which comes under the control of the Legion. Their programming being switched eventually caused Rusty and #4 to swap bodies; in #4's body, Rusty destroys the second Nova. •
Bad Guy (voiced by Jonathan David Cook) – A fully robotic clone of Big Guy also known as the BGY-11X. Created to take Big Guy's place to infiltrate the military and Quark. It fights it out with Big Guy who proves to be no match for it, although both robots take heavy damage in the fight. The 11X is destroyed when Lt. Hunter fires Big Guy's hand into its cannon, blocking the shot and causing an explosion. •
Lt. Hunter Clone – A robotic clone of Lt. Hunter sent to kidnap him and wipe out his mechanics and Doctor Slate. It was destroyed by Rusty, who threw it into a helicopter propeller, causing it to fall off Quark and crash into Donovan's new limo. •
Dr. Neugog (voiced by
Tim Curry) – Hieronymus Neugog is a scientist working at Quark Industries who studied telepathy and the inner workings of the mind. Neugog created a machine known simply as the "Dynamo", which was designed to read the mind of whoever it was homed onto. Neugog attempted to impress the board of directors by reading the mind of a board member. However, a
spider falls into the machinery and mutates Neugog into a huge, spider-like monster with an oversized brain. Neugog can devour brains via his
proboscis, which allows him to assimilate knowledge. When Neugog feeds, the victim is put into a comatose state where they are unable to speak, move, or think. •
Big Rig (voiced by
Ron Perlman) - A thug in a robotic suit with missiles. He tried to blow up the Lincoln Memorial before surrendering upon Big Guy's arrival. In "The Big Boy", Big Rig appears as a member of the Chopshoppers. This time, Rusty managed to defeat Big Rig and his unnamed teammate. •
Earl (voiced by Pamela Adlon) – Earl (E.P 327) is an early prototype of Rusty. He has an underdeveloped emotion grid and follows orders literally. Initially brought back online by Rusty for him to have a friend, but after he goes too far and blows the Big Guy's head off, Rusty fights him and manages to decapitate him and remove his powerpack. ==Episodes==