Farscape S02 E11 Look at the Princess - A Kiss is But a Kiss (1)

"My name is John Crichton, an astronaut. I'm just looking for a way home."

Moya arrives at a planet where the population test their genetic compatibility by kissing. Crichton kisses a princess, who is next in line for the throne, and discovers that his DNA is a perfect match for her. He must now marry her and they will rule together.