Cogenitor (Season 2)
"I always say that the best episode we ever did was 'Cogenitor'," Keating said.
Here, the crew meets the Vissians, a race that has a third gender, which is in the minority. This cogenitor is only used to help the other two genders reproduce. Commander Tucker tries to fight for the cogenitor's rights, but it doesn't turn out the way he hopes in the end.
"It's not just an incredible sci-fi episode, but just a good episodic episode," Keating said. "It's one of our finest episodes."