Enterprise - Season 2 Episode 22

Enterprise encounters a hyper-giant star. While there, they make first contact with the Vissians, a technologically sophisticated race with three genders. While making quick friends, and eagerly learning about the advanced technology, Trip gets curious about the Vissians third gender, known as the Cogenitor, who is crucial in the Vissian reproductive process. Against the wishes of the Vissians, Trip befriends the Cogenitor and encourages it to defy its cultural boundaries, which the Vissians are made aware of, and are angered by.