Ranpou embodies chaotic mischief, relentlessly pursuing voyeuristic thrills centered on his teacher, Miss Iwasaki. His signature cry, "I saw it! I saw it!", erupts after glimpsing her underwear. This core trait fuels interactions defined by escalating absurd scenarios. One incident saw him consume excessive pepper, breathe fire, and ignite a building, followed by trespassing in the women's bathhouse section and draining an entire tub.

He operates alongside Chutaro, a genius talking mouse whose inventions facilitate their misadventures. Their exploits feature surreal physical comedy: swimming through classroom desks during chases or wielding laser guns against giant ants, causing widespread destruction like leveling parts of Tokyo. His girlfriend Mutsumi, who witnessed his transformation, and his long-suffering guardian Mr. Kakumaru—a teacher harboring a crush on Miss Iwasaki—routinely become entangled in his chaotic schemes. Residing in Mr. Kakumaru's apartment further strains their relationship.

Ranpou thrives on parody, weaving references to 1980s pop culture icons like Godzilla, Ultraman, Captain Harlock, and Nausicaä into his antics. One episode featured a virtual reality sequence mashing elements from multiple sci-fi classics. His stories prioritize escalating absurdity over narrative coherence, exemplified by an opening sequence casually depicting Ranpou crushing multiple iconic monsters mid-brawl.