Killy Gagley hailed from the Bronx, bringing his street-smart gangster background to the Good Thunder team. As one of the three primary pilots of the super robot GoShogun, he operated the jet Jack Knight, docking within GoShogun's right leg for combat. He directly engaged the antagonistic organization Docooga in missions across global locations.

Personality-wise, he maintained a tough, pragmatic demeanor forged by his urban upbringing, often employing streetwise tactics in battle. Despite his generally gruff exterior, he occasionally displayed humor and engaged in light banter with teammates during combat, revealing underlying camaraderie. His interactions with the young Kenta Sanada included mentorship moments, though he expressed initial annoyance at the boy's curiosity-induced troubles before gradually accepting him as part of the crew.

Decades after the original conflict, he appeared in the sequel film *The Time Étranger* as a middle-aged man, gathering at the bedside of his comatose former teammate Remy Shimada. This appearance demonstrated his continued connection to the original team members and implied his later life involved business ventures, specifically co-founding the fast-food chain "Kernagul's Fried Chicken" with his former adversary Yatta-la Kernagul.