Hermaphrodite

In biology, a hermaphrodite was an organism which could not be easily classified as belonging to a "male" or "female" sex.

Alpha Centaurans were hermaphrodites, sometimes referred to as "it". Nevertheless, the Third Doctor generally used masculine pronouns to refer to the Federation ambassador to Peladon. (TV: The Curse of Peladon)

Chelonians were hermaphrodites and all members could lay eggs. Despite this, Chelonians were referred to as males. (PROSE: The Highest Science)

The Sloathes, (PROSE: Sky Pirates!) the Brascans ,(PROSE: Kursaal) and the Torcaldians (PROSE: The Ruins of Time) were also hermaphrodites.

Circa 2360, it became popular among humans to become hermaphrodites. In 2363, the fad ended. Wanting to find a way to quickly populate colony planets, the Earth government conducted experiments in super-fertility with some of the hermaphrodites. (PROSE: Dead Romance)

Behind the scenes
In the real world, "hermaphrodite" is considered an antiquated, even offensive term, when applied to humans. The correct modern-day term is.