Ronnie serves as Corporal in Patrol A3, a Galactic Federation team sent on reconnaissance to Earth to evaluate its threat to interstellar peace. Their critical objective involves determining whether humanity warrants destruction via deployment of an anti-proton bomb. Operating undercover alongside teammates Bokko and Pukko, Ronnie adopts the form of an orange-brown horse based on captured Earth specimens. This equine disguise conceals advanced physical capabilities, including disproportionate strength and speed. His role emphasizes technological proficiency, showcasing exceptional aptitude for rapidly constructing functional machinery from scavenged materials, notably the versatile Big Wheel vehicle capable of high-speed travel across land, water, and air.

Personality-wise, Ronnie exhibits pragmatic tendencies distinct from his teammates and displays notable enthusiasm for Earth's culinary offerings. This appreciation contributes to his gradual shift in perspective regarding humanity's value, contrasting with Pukko's persistent advocacy for planetary destruction. Ronnie maintains a romantic connection with Felina, another Galactic Patrol agent in feline form on Earth. His terrestrial activities include forming an alliance with Shinichi Hoshi, a human boy aware of their true nature, and Shinichi's older brother Koichi, a member of the intelligence agency Phoenix. Ronnie assists Phoenix operations against threats like Interspy, employing his technical skills.

Character development reveals evolving attitudes toward humanity, particularly during the mission's critical phase. When the Galactic Federation orders Earth's destruction, Ronnie supports Bokko's decision to defy the directive. He accompanies Shinichi to the aliens' homeworld to plead humanity's case before the council. Following the council's agreement to postpone judgment, Ronnie participates in Bokko's transformation into a human girl, facilitating her desire to remain with Shinichi. This narrative progression concludes with Ronnie continuing Earth-based operations alongside the team under the Galactic Federation's temporary reprieve for humanity.