They are an experiment on the planet Keron in order to create Keronian super soldiers and they gave the Keroro troop (without Dororo knowing it [they once again forgot about him]) the first prototype, as Earth was a safe place to test their capabilities.
The problem is that the prototype was strange to how they imagined it, very distracted, quite quiet, it got sleepy and when it came to having to answer it was very difficult for him, being very nervous about wanting to show her capabilities and not being able to do, so, the troops decided to stop this situation and they ended up leaving her alone, going to the base to report that they should return them to Keron, at that moment the prototype overthought things a lot and entered a state of uncontrollable overwhelming thinking that he had failed his companions and her creators, making him in that state, transform into her most savage version by her own most vile and crazy thoughts, she sought revenge to sink everything based on the brute force of their arms, thus demonstrating, according to her,superiority and worth for the army against the inept of the troop, being out of control.
It was there when the troops heard the noise and chaos that Shippy was trying to generate, from simple pranks to wanting to harm humans and things of the city, there they decided to defeat her because of the disaster that could cause and although it cost them a lot, thanks to the appearance of Dororo at the last moment, they managed to knock her out and save her from a fall.
There the troop went to notify their superiors while Dororo watched over her, and when they woke up, both sharing a small conversation, Shippy felt very sorry for what had happened and when Dororo asked her why he did all that, she explained that she did not want in true, but rather those thoughts of her own possessed her at her weakest moment, when she thought of having failed all, being a twisted side that she was not proud of having and he did not want to return to the planet because there they would surely throw her away. Dororo, very empathetic, understood and he went to the group to interrupt said conversation with his superiors so that they would give her the opportunity to continue, only for when he interrupted, his superiors said that the project had been canceled due to lack of a proper budget and that they would be left with Shippy and dealing with his problem, shrugging their arms when Keroro asked how they have to do that and hanging up the call after that.
So, Shippy stayed with the Keroro troop, living in the Hinatas' house, as it was the best place where they could keep him under watch and in constant company, since if she is left alone, that state of overthinking things returns and they would be out of control again.
Maybe one day she can feel completely in tune with her thoughts and find peace while adapting to the meaning of feeling happy with her friends and probably even more...
Hope ya all love the desing,ill still do art of the usual but i wanted to create a sona for this childhood series of mine as i been rewatching it,so,i hope you don't mind!💖
Boom that how this little guy appear/born anyway- as mention they are Grey tree frog I will do actual character sheet later(?) since this is my friend keroroOC! It going to take sometime to come up with a proper backstory and well draw because they are picky with the design