Korby used the android duplicator to make a very close copy of Captain Kirk, and though initially intended only to impress Kirk and gain his cooperation in exploiting a new planet, the duplicate served to impersonate him once Korby realized his cooperation was not forthcoming.
During the copying of his memories into the android, Kirk had held a marked antagonism towards his first officer in the forefront of his consciousness, repeating the phrase "Mind your own business Mr. Spock! I'm sick of your half-breed interference, do you hear?" Aboard the Enterprise on a mission for Korby, the duplicate used Kirk's phrase in order to avoid Spock's observation. As it was, however, completely out of character, the phrase alerted Spock to the fact that his captain was in trouble.
Back under the surface of Exo III, the android duplicate was destroyed by Andrea when it rebuffed her sexual advance, terming her wish to kiss "illogical". She was armed with a phaser gun, since Korby had just ordered her to protect the cavern base from Spock's landing party. (TOS: "What Are Little Girls Made Of?")