Thrasher and Blastus are two outsider robots that live on the planet Insanus. Insanus is a planet inhabited by murderous robots who seek to kill one another for no apparent reason. Slightly less horrific than their peers, the duo seek to make it through high-school, and navigate their lives with varying degrees of sucess. While Thrasher wishes to gain the affections of an attractive female robot Maimy, Blastus just wants to be recognized as popular. Three girls Emily Omika, Frankie Lizzar and Alice Benar are getting away from school.
- Thrasher (voiced by Patton Oswalt) - A tall, lankly robot who isn't very confrontational and has a crush on the popular female robot Maimy. Thrasher has a baby sister, who is considered very violent and dangerous towards him and others. Though calm and reserved, he often falls prey to Blastus' badly-thought out plans.
- Blastus (voiced by John Gemberling) - As with Thrasher, and unlike most robots on Insanus, Blastus is a pretty sensitive and non-homicidal, to which his mother doesn't approve. In his quest to become popular, he is incredibly impulsive and overconfident in his abilities.
- Weenus (voiced by Michael Sinterniklaas) - A nerdy robot that is even lower on the social pyramid than the two main characters, Weenus is a bi-polar sociopath, whose giant arm is thought to be the most powerful weapon on the planet.
- Dreadnot (voiced by Dana Snyder) - A sadistic teacher that finds joy in torturing and invoking pain into his students: all in his attempt to transform them into hyper-violent drones.
- Megawatt (voiced by Michael Sinterniklaas) - A spoiled rich kid at Harry S. Apocalypse High, Megawatt is quite dim and incredibly homicidal, which makes him attractive to female robots.
- Maimy (voiced by Jessie Cantrell) - A popular student at Harry S. Apocalypse High, Maimy is Thrasher's crush, but she is barely even aware of the robot's existence and even then, would rather claw-out his face. She has a baby brother with a deeply-demonic voice.
- Thunderbite (voiced by Dana Snyder) - An oversized, skull-shaped robot, who is the principal of Harry S. Apocalypse High School, and is incredibly sweet and motherly to the students when he isn't causing pain. He is good friends with Thrasher and Blastus.
- Tacklebot - A strong, burly robot who's part of the football team. He is usually being seen bullying the smaller robots by beating them up as a way to make him feel stronger. He will always be randomly attacking Thrasher and Blastus out of nowhere just for the sake of being abusive so that he will feel strong.
- Steve - A robot that will recurrently make random appearances in episodes of the show. He is a mentally challenged robot with many arms that he uses to destroy things with. He is very naccrosistic and loves everything he does. He is however, unaware of how much destruction he causes while doing this. In he end, he always seems to somehow pull though and make things right, no matter how horrible he makes he situation.
- Emily Omika (Laura Pero) is the best girl on the field. She noticed that she had a very strong power of length. She is very good at all the good times she has sent.
- Frankie Lizzar (Emma Insley) is the only good girl who is a special person.
- Alice Benar (Cal Jaggers) is the greatest girl to play with Frankie and Emily.
For the full list of Robotomy episodes, see List of Robotomy Episodes