Nevula is a supporting character in the anime Sgt. Frog, known in Japan as Keroro Gunso. He serves as the adoptive father of the character Alisa Southerncross and is almost always seen in a peculiar form: he takes the shape of cat ears that sit atop Alisa's head, though when he is not in that form, he appears as a spherical object about three feet in diameter with cat ears and a single red eye. His background is that of an alien being who cares for Alisa as his daughter, and his primary motivation is to transform her into a fully human being, a goal he actively pursues throughout his appearances. Nevula's personality is deeply protective and parental, and he exhibits strong separation anxiety when he cannot be near Alisa, as seen in episodes where the group visits a hot spring and he struggles with being separated from her by the gender-segregated bathing area. His role in the story is that of a supportive but somewhat fretful guardian who accompanies Alisa in her interactions with the main cast, often adding a layer of comedic tension through his overprotectiveness. His key relationship is with Alisa, whom he treats as his child, and he interacts with the Keroro platoon and the Hinata family primarily through this bond. While his character does not undergo major development, his consistent devotion to his daughter and his quirky appearance make him a memorable minor figure. Notably, Nevula possesses the ability to change his shape between the cat-ear form and the ball-like state, and he also appears to have some form of awareness and mobility even when attached to Alisa's head.