Kero 0: Shuppatsu da yo! Zenin Shuugou!
Keroro Gunso Episode 0 ／ Keroro Gunsou: Kero Zero - Shuppatsu da yo! Zen’in Shuugou!! ／ Keroro Gunsou: KeroZero Shupattsudayo! Zeninshuugou! ／ Keroro Gunsō: Kero Zero - Shuppatsu da yo! Zen’in Shūgō!! ／ ケロロ軍曹 ケロ0 出発だよ！全員集合！！ ／ ケロ０ 出発だよ！全員集合！！
Description
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.