Plot

On a planet called Keron live a race of froglike aliens, known as Keronians. Ordered by their planet's army, a platoon of five head to Earth in hopes of conquering the planet for their own. All hopes of invasion are stalled when the leader of the group, Keroro, is captured by Fuyuki and Natsumi Hinata in Tokyo. In exchange for housework, he is permitted to carry out his plans from their basement. Over time, his four comrades - Tamama, Giroro, Kururu, and Dororo, alongside his helper Mois - reunite and assist him in his plans for domination. Everytime they seem to succeed, Natsumi, or another person, finds out about the plan and thwarts it, leading to failure.

Alongside the main story are several arcs and side stories.  Many of the chapters and episodes that do not focus on invasion plans are slice-of-life stories concerning the aliens and their human friends, such as going to Kyoto or the beach, often with extraterrestrial twists. Other segments deal with Keroro, Giroro, and Dororo (then known as Zeroro) and their childhood misadventures. Others contain one or a group of characters reaching a goal or solving a conflict unrelated to the invasion plans, such as fending off the Shurara Platoon in the eponymous arc.