Coo Erhard holds the rank of major in the Black Gema Gema Corps, an antagonistic faction within the series. First appearing during the Christmas Special alongside fellow operatives, he combines his role as a skilled physician with a youthfully unorthodox presence, though his medical training remains undefined. His design adheres to the group’s animal motif, featuring a canine tail and a cap shaped like a stylized dog’s head. Short, dirty-blond hair frames his reddish-brown eyes, creating a distinctive silhouette among his peers. Coo’s personality blends a default calmness with flashes of selfishness and defiance toward authority, often reacting to commands with bratty resistance. This contrasts sharply with more explosive personalities in the series, anchoring him as a secondary antagonist whose clinical efficiency and subdued unpredictability maintain his role within the Corps. Subsequent media iterations preserve his established function without expanding his backstory or narrative impact beyond these parameters.