The protagonist of the story, a dim-witted alien who came from Planet Peke Peke to conquer Earth. While he looks cute, he carries numerous gadgets powered by super-science that could easily conquer Earth if used correctly. However, due to his extremely airheaded and thoughtless personality, he fails to use them properly every time, causing chaos and dragging everyone around him into the mess. Rather than being a villain, he is pure, childish, and somehow lovable. His slapstick daily life with Rui and Hayato is the charm of the series.

A perfectly ordinary middle school student living on Earth. A top student who is good at studying and possesses vast knowledge, he teaches various things to Pekets, who knows nothing of Earth's culture or common sense. He lives with Pekets to monitor him and prevent the conquest of Earth, but he is a chronic sufferer who gets caught up in Pekets' rampages every time. He supports the story as the calm straight man, often resolving incidents with the judgment expected of a sensible person. Despite his constant complaining, he shares a deep friendship with Pekets.

A boy who attends the same middle school as Rui. He is athletic and good-looking, but he is a "disappointing handsome guy" who thinks of nothing but wanting to be popular with girls. He frequently tries to use Pekets' gadgets for his own desires, which invariably leads to unexpected trouble and results in him suffering a terrible fate. Although he is bright and proactive, he is a bit simple-minded and a show-off. He is a popular character who dives into the chaos alongside Pekets and Rui, making the story even more lively.

A middle school girl with blue short hair in the same class as Rui and Hayato. She is often followed around by Hayato and occasionally gets dragged into their troubles.

The homeroom teacher of Rui's class. He wears glasses and is generally strict; he views Hayato as a problem student and often lectures him.