Nevula commonly takes the shape of cat ears on top of Alisa's head. When not, he takes the shapes of a 3-foot diameter ball with cat ears. He only has one eye, which is red in color. He was created by the spirits of inhabitants of a destroyed planet, revealed to be the only living member of his species.
Nevula is able to shape shift into many different forms, though he always leaves a part of himself with Alisa. In addition, he can become a set of functional destiny wings.
- Alisa Southerncross - Alisa is Nevula's adoptive daughter. After his home was destroyed, he needed a living thing to live. He brought Alisa to life, and has since then never left her. Nevula loves Alisa deeply, worrying when monsters appear too dangerous to capture. Alisa herself loves her father, worrying when Angol Mois makes him retreat back into her ears.
- Shin Keroro - Former prey
- Akuaku - Former enemy
- Aki Hinata and Keroro - Friends
- Angol Mois - Nevula has a great fear of Angol Mois, due to the fact she "destroyed his home planet". Upon reveling her true form, when they first meet, Nevula freezes up and has to revert to Alisa's headband, due to his fear. It was later revealed that Angol Tia, Mois's mother, was the one to destroy his home.
- In the flash series Nevula doesn't always rest on Alisa's head and he is usually seen as some other shape (i.e. a TV).
- Nevula is based on the real space Nebulas, which are large clouds in space where stars are born.