Robot is first thought to be nothing more than a robot with advanced artificial intelligence who leads the Teen Team. As it turns out Robot is really just a machine controlled by the mind of genius Rudy Conners. Rudy was physically unable to live outside of a specially built pod because the air would burn his skin, so he created Robot to live vicariously through. Rudy now exists outside his tube as a clone of Rex-Splode, and still controls robot with his mind. There are multiple version of the Robot automation used for different situation.
In Invincible Ultimate Collection #1 Robert Kirkman says
Robot was all Corey [Walker's] idea... I really just came up with the know-it-all personality to go with the design.
Major Story Arcs
Robot was a member of the Teen Team, who helped Invincible defeat one of the Mauler twins. Now much was known about him, other than the fact that he had vast intelligence and some fighting skill. Robot later wiped the Mauler twin's memory and used him to lead himself, Atom Eve and Invincible to the twins' lair, where they apprehended the Mauler twins. Later, Robot was investigating a series of mall bombings and discovered the identity of the bomber, sending Mark and Eve to take down Mr. Hiles, their physics teacher.
Guardians of the Globe
With the death of the Guardians of the Globe at the hands of Omni-man, Robot was appointed leader of a new team by Cecil Stedman and told to hold trials for new members. The new team was chosen and the new Guardians were underway. Eventually, it became apparent that Robot had feelings for Monster Girl and tried his best to fix her problem. Once Black Samson was put into a coma by Battle Beast, Robot decided that Monster Girl would use his old suit rather than transforming. After an invasion attempt that the Guardians failed to thwart, Cecil removed Robot from the leadership position and offered it to the Immortal, also bringing Bulletproof into the team.
Around this time, Rudy secretly used his Robot to take a DNA sample from Rex-Splode, having seen how Monster Girl was attracted by his appearance. He enlisted the help of the Mauler twins to help implant his mind into the clone, which was engineered to be younger than Rex, but in the end Rudy ended up as two beings, one mind in the Rex clone and another in the original body. Rudy allowed his original body to die and promptly turned on the Maulers, using his Robot constructs to take them down. By this time Monster Girl had accidentally destroyed Samson's suit and Rudy revealed his true identity to his team. Amanda was pleased that she would finally have someone to hang out with in her down-time, without getting any weird looks, now that Rudy also looked like a kid.
The two went to see movies and went on dates and eventually became very close. They both remained active members of the Guardians of the Globe and Robot continued to try and find a cure for Amanda. They were both chosen to go into space and attempt to stop the sequid invasion, where Robot was a key player and found a way to disrupt the mental link the sequids shared. He then created a device to separate them from their host, Rus Livingston, allowing the Guardians to bring him safely back to Earth.
After Cecil turned against Invincible, Robot was one of the Guardians to help their friend and leave the government-sanctioned Guardians of the Globe. Along with Monster Girl, Rex-Splode and Bulletproof, Robot set up shop in the old Teen Team base. During that time, Invincible found a device that was monitoring his family and brought it to Robot for analysis, after it self-destructed. The technology was extremely advanced, almost other-wordly, and Rudy was unable to determine who was monitoring Invincible. However, he did make a breakthrough with Monster Girl's condition, creating a belt which would take a copy of her cell structure seconds before each transformation occurred, effectively stopping her de-aging.
After Rex-Splode's death during the events of Invincible War Rudy had is name legally changed to Rex to honor his friend's sacrifice.
The Flaxan Dimension
When the Flaxans retreated after another failed invasion attempt Robot, accompanied by Monster Girl, had followed the Flaxans through the portal to their own dimension in hopes of defeating them for good.
They where captured and Imprisoned by the Flaxans almost immediately after they entered their dimension, but due to how time passed slower for them than for the Flaxans he was able to plan an escape over the course of twenty years. During this time Rex was able to learn the native's language by monitoring radio transmissions. He also learned that the Flaxans planned on enslaving the population of Earth like they had done to several other races and task them to rebuilding their jewel city Klaxia that had been destroyed by Omni-Man centuries before. When their escape, and subsequent attempt on the life of their Emperor failed, Rex and Amanda were charged with rebuilding Klaxia alone as punishment. But seeing the progress that was made the Flaxans eventually began sending in hundreds of slaves to aid them, and as generations passed the slaves rallied behind Rex, which is what he had planned from the beginning, leading them in a revolt against the Empire. As the rebellion escalated other Flaxans began to join the fight against the ruling Zaxal royal family.
After centuries of war the rebellion was eventually a success and Rex was chosen as the ruler of the Flaxan dimension, and although he and Amanda had the ability to return to Earth, after confessing their love for each other they decided to stay and build a life together on their new home.
Though they where happy together Rex, burdened by the responsibilities of this rule, began to neglect Monster Girl and their relationship began to weaken for several reasons. When Monster Girl discovered the hash treatment of members of the Zaxal family she began to openly appose his decisions regarding the matter; and after a falling-out she left him, living with the oppressed members of the Zaxal family and their allies for almost two decades. Shortly after she returned their relationship continued to degrade due, in part, to Rex's inability to give Amanda a child.
When the the twin heirs to the Flaxian throne, Zull and Zall, attempted to overthrow Rex Amanda betrayed him and sided with Zaxals, imprisoning Rex. After years passed Amanda became lonely in Rex's absence, and gave Zall a child through her Monster form, though she was unaware that it was actually possible, but when the twins mounted an attack on another dimension Amanda freed Rex and together they foiled the twin's invasion attempt.
Though they made amends after this Rex and Amanda decided to return to Earth and try to forget the pain the Flaxan dimension had caused them.
Robot is voiced by Stan Kirsch in the motion comic of Invincible.