Niki was a 23rd century Oordon native man.
History[]
In 2266, Niki was exposed to de-aging radiation released by an earthquake, and after 193 days of exposure he was one of the few surviving inhabitants of Oordon, reduced to the equivalent of a one or two year old humanoid.
He was being cared for and fed by Elya in a nursery. Leonard McCoy noticed that he had a cut on his right elbow. When McCoy reached to take a closer look, Niki bopped him on the head with a rattle.
Later, Montgomery Scott sat Niki on his knee and started reciting the bedtime story of Colonel Goldilocks and the Three Gardazian Bears, but the young boy soiled his diaper before Scott could finish.
After the source of the radiation was buried, Leonard McCoy brought Elya and Emperor Wenomi an antidote that would restore Niki to his proper age, but Elya preferred that he and the other survivors grow back to adulthood naturally, giving them more time to restore their civilization. (TOS comic: "World Against Time")