Hermaphrodite

In biology, a hermaphrodite was an organism that had reproductive organs normally associated with both male and female sexes.

Despite their female-sounding voices, Alpha Centaurans were hermaphrodites and properly referred to as "it". Nevertheless, the Third Doctor generally used the masculine 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 Crystal Bucephalus)

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)