Taruru

Taruru used to be Tamama's apprentice, and still calls him "master," or "senpai," meaning his superior, Taruru was more clumsy than Tamama in the past. Taruru was a blue Keronian tadpole who's symbol is an orange and yellow raindrop shaped emblem, the mark of an "old driver" in Japan, but he matured faster, in his appearance in volume 10/episode 101, he had adult features instead of tadpole features. Taruru first appeared to see if all the rumors about the Keroro Platoon was true, revealing what Tamama told him about the platoon. In the anime he also appeared a couple of times with his childhood friend Karara, forming a duo of mischievous tadpoles. Despite Taruru's clumsiness in the past, he had become very skilled when training in the Garuru Platoon and has skills that exceeded Tamama's, defeating him in a face-off. He then captures Momoka and Paul, then later on also captures Mois. After Keroro encourages his platoon to rise Tamama, after receiving power from the Super Rhinocerous Beetle, returns for a rematch and Taruru is defeated. Source - Wikipedia