Brown (android)
The android duplicate Doctor  was created from the body of the 23rd century Federation scientist. This android was created around 2261 by Dr. Roger Korby and Ruk from the records and machinery he found left behind on the planet Exo III by . 

Brown was sent to retrieve the  landing party, consisting of James T. Kirk and an old acquaintance, Christine Chapel, in the underground ruins after they had beamed down to Exo III in 2266. As soon as Brown was discovered, the sound of Mathews falling to his death was heard, prompting them to return to Mathews' last known location. Though "Brown" was aware of the true nature of Mathews' death, murder by Ruk, he urged Kirk and Chapel to be careful as they peered into the bottomless pit, informing them that he must have slipped and that there was no hope for his recovery.

Following the accident, considering "Brown"'s callous response combined with his somewhat indifferent response to seeing his old friend Chapel, Chapel felt "Brown"'s reaction to seeing her was less than she expected. When Kirk noted this, she attributed it to five years spent in the dark ruins of Exo III.  

As "Brown" escorted Kirk and Chapel, he explained some of the basic aspects of what Korby had discovered on Exo III. Once they arrived and he introduced them to Korby, Korby required that Kirk not communicate with his ship, leading "Brown" to pull a phaser to threaten Kirk. During the brief standoff that followed, "Brown" was shot at close range by Kirk, damaging him enough to render him inert. 

After it was revealed that like "Brown," Ruk too was an android, it explained that the latter was "more complex than 'Brown'; much superior." ()

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Androids