Urusei Yatsura (1981)

Season 1: Episode 131

Ryunosuke loses the cloth that wraps up her breasts, but decides to not buy a new wrap when she's finally treated like a girl by everyone around her. But when it comes time to play rugby at gym class, the boys are more interested in Ryunosuke's large chest than they are in playing the actual game. At the same time, an evil space queen and her all-male henchmen are plotting to overtake Earth, their ship the size (and shape) of a rugby ball.