A planet run by women whose technicians overhauled the Enterprise computer and gave it a flirtatious female personality, a running joke in the episode Tomorrow Is Yesterday.
Cygnet XIV is mentioned in the Original Series episode Tomorrow Is Yesterday. Shortly before the story begins, the Enterprise put in there for general maintenance, and the planet's technicians took the chance to work on the ship's computer system.
Spock explains that the society of Cygnet XIV is dominated by women, who felt the computer lacked a personality and supplied one. As a result the machine answers in a sultry voice, giggles and addresses the captain as dear.
Kirk is embarrassed when it does so in front of Captain John Christopher, the twentieth-century pilot brought aboard after his aircraft is destroyed. Spock notes that putting it right would need a complete overhaul at a starbase, so the crew has to live with it for a while.