Keroro Gunsou: KeroZero Shupattsudayo! Zeninshuugou! is a special anime that premiered in spring 2009.

About the production: there is 1 episode of about 15 minutes and its current status is "finished".

Its main genres are action, adventure, comedy and mecha, with themes such as Aliens.

On AniList, Keroro Gunsou: KeroZero Shupattsudayo! Zeninshuugou! has an average score of 62%, an average score, and appears on 724 users' lists.

This is episode 0, the prequel to the main Keroro Gunsou anime series. KeroZero was shown in theaters with Keroro Gunsou Movie 4. On the day of Keroro battalion's departure from Keron Planet to Planet Earth, an opposing alien species assails the Keron space station, where Giroro and Zeroro (later known as Dororo) are waiting for Keroro to arrive.

Official synopsis from AniList.