Protoboy is created by Professor Moshimo. He is also Katie's ex-boyfriend. He is one of the antagonists in the series, and the main antagonist in the special Robotboy: Dawn of the Robot Clones, He is one of the secondary antagonists turned anti-hero in the first live-action film. He is also one of the tritagonists of the 2nd live-action film and the film Robotboy and the Titanium Quest. He is voiced by Rupert Degas. In the live-action films, and in Season 6, he is voiced by Crispin Freeman. In the films, he is voiced by Nick Jonas.
Professor Moshimo created Protoboy many years ago after getting out of the academy. But because of the Professor's young age, Protoboy lacked humanity and was quite vicious. He was later kidnapped by a young Dr. Kamikazi who turned him evil so he could rule the world, but he made him too evil, to which Protoboy was deactivated after being defeated by Constantine.
After Robotboy attempts to resurrect him, Protoboy becomes full of rage and decides to destroy everything near him. Robotboy tries to be nice to him, but Protoboy doesn't stand for this. He shows disdain for Robotboy`s friendship, and attempts to "destroy" him and win back Katie.
Robotboy sees Protoboy as a friendly Robot, with a bit of a temper. Robotboy becomes so clouded by Protoboy`s position as his "brother" that he doesn`t understand the true cause of it.
Not a very good relationship together with Tommy since he doesn't see him as a good person to him. He almost destroyed him on five occasions, two in "Brother", two in "The Revenge of Protoboy" and one in "The Return of Robotgirl".
A very bad relationship, in the episode "The Old Switcharobot" when Protoboy was inside Robotboy's body he punched Gus right out of Tommy's window when Gus was trash-talking him. In "The Return of Robotgirl", he came close to killing him for tricking him that he's another one of Moshimo's robots.
In the episode "The Revenge of Protoboy" he spoke on his cellphone to his dear (as he calls her). Although it is unknown which character he spoke to but it could've possibly been his girlfriend since he gives her a kiss when he had finished speaking to her.
- In Protoboy's debut episode "Brother", his flames while flying were orange like Robotboy & Robotgirl, but in his later appearances his flames are blue.
- Also, in "Brother", Protoboy's vocabulary is quite flat (he mostly says "Destroy") & his voice was also a bit deeper more robotic and more garbled, but in later episodes his vocabulary got better his voice becomes lighter and more monotonic.
- His eyes are in the same shape seen in Robotboy's Superactivated mode.
- Unlike Robotboy who doesn't speak when he's Superactivated, Protoboy can speak clearly when he's Superactivated. In fact, when Robotboy was in Protoboy's body (from "The Old Switcharobot") he didn't speak at all when he Superactivated in Protoboy's body. This could be due to his habit of not speaking in his own Superactivated mode.
- Protoboy has two different appearances when he's Superactivated, one is his regular and the other with a big gun appearing from his back and while preparing appears more red. This version only appears for a short time in The Revenge of Protoboy.
- According to Jan Van Rijsselberge, Protoboy was not Robotboy's only prototype, there were a few experiments, but non were fully operational, and thus didn't get a name.
- How Protoboy got repaired is unknown for the moment, but there could be a hint that someone really is repairing him after he gets destroyed, especially the one he spoke with on his phone (which could be his girlfriend or wife since he calls her; "Dear.") This may also explain how his voice and flames while flying are different. Aswell as his insides in The Revenge Of Protoboy being grey instead of yellow.
- The idea of a prototype brother may be inspired by Proto Man from the Mega Man series.
- The evil personality and gold coloration for a brother might be inspired by Atlas from the 80's version of Astro Boy.
- Protoboy has so far only appeared in 4 episodes which are the following; "Brother", "The Old Switcharobot", "The Revenge of Protoboy" and "The Return of Robotgirl."
- His last words in the series were "Not finished, yet!!" (the last word was cut due to being shot by a Superactivated Robotboy).
- Interestingly, there's never been an episode involving Robotboy in his deactivated mode where Protoboy appears.
- In the Powerpuff Girls crossover fancomic Powerpuff Girls Doujinshi. He is a minor villain. He can be seen here.