Pierrot the Human, son of Colonel Pierre and President Pierrette, originates from "Once Upon a Time... Space." He later joins the crew of "Seimei no Kagaku Micro Patrol" as a central character. Alongside his friend Psi, he patrols the intricate biological systems within the human body.

His visual design maintains continuity from prior series, featuring science fiction-inspired attire specifically suited for navigating microscopic internal environments. Pierrot operates specialized patrol vehicles to monitor vital bodily functions and swiftly respond to threats like invading pathogens.

Within the context of biological defense, Pierrot and his companion act as proactive agents combating viruses and bacteria, collectively known as "the bad Characters." Their activities involve close coordination with anthropomorphized immune cells and other entities representing bodily functions to maintain health.

Pierrot's narrative function centers on illustrating complex biological processes through accessible scenarios. He participates in episodes demonstrating immune responses, blood circulation, and organ functions. His interactions directly facilitate educational explanations of medical concepts, such as antibody production and infection containment.

No substantial personal evolution or backstory specific to Pierrot is documented across the series' episodes. His role remains consistently focused on these educational demonstrations rather than character-driven development.