However, the first truly successful androids in the Federation were the Soong-type androids created by Doctor Noonien Soong. Most notable of these was Lieutenant commander Data, who served as operations officer on board the USS Enterprise-D and USS Enterprise-E. (Star Trek: The Next Generation)
Types of androids
Automated Personnel Units
In 2372, the USS Voyager found a deactivated android which, upon repair by B'Elanna Torres, identified itself as Automated Personnel Unit 3947. It used Torres' goodwill to gain sympathy for his "people", who were on the verge of extinction after the death of their creators, the Pralor. It was later found that a people known as the Cravic had also made Automated Personnel Units, and that the Cravic were also extinct. Originally, the two peoples had been at war, using the Automated Units to battle. However, when the war ended and it was time to dismantle the APUs, the robots, not understanding anything except war and self-preservation, wiped out their creators and resumed their war. (VOY: "Prototype")
Exo III androids
A sapient species on the planet Exo III, now known only as "the Old Ones", discovered how to build sophisticated androids thousands of years ago. They made their machines more and more complex, eventually conferring upon them the ability to feel emotions. Their greatest technical achievement was perhaps the android duplicator, a mechanism that could manufacture an exact android duplicate of a living being, including that person's memories.
The Old Ones built their machines too well; according to a surviving machine, Ruk, the Old Ones became afraid of their machines and began to deactivate them. Their survival threatened, the machines overcame their programming and slew their builders. Ruk and all other known Exo III-type androids were destroyed in 2266. (TOS: "What Are Little Girls Made Of?")
- See: Rayna Kapec
The Ilia probe was an android created by V'Ger to gather information about the carbon units aboard the refit USS Enterprise. It was a highly complex construct built out of the body of the Deltan, Lieutenant Ilia. As a side effect of being made out of a living humanoid, it retained many aspect's of Ilia's personality, including pheromones, memories, and ultimately her emotions. It contained molecule-sized microprocessors and billions of connected mechanisms. (Star Trek: The Motion Picture)
A Class K planet was inhabited by thousands of advanced androids originally from the Andromeda Galaxy. Their makers had established outposts throughout their own galaxy, and had built only a handful of outposts in the Milky Way Galaxy; however, when the sun of their home star system went nova, most of their civilization was destroyed. The remaining makers died out over time, leaving only distant outposts of androids.
These androids had their first encounter with native life in the Milky Way when infamous criminal Harcourt Fenton "Harry" Mudd, having escaped from imminent execution on Deneb V on charges of fraud, fled known space and crash-landed on their planet in 2268. Mudd was hardly an ideal model of Humanity, and the androids decided that Humans were a form of galactic pest that needed to be contained for their own protection (and the protection of the galaxy). These androids could have an operational lifespan of up to 500,000 years, and had access to advanced medical technology which could let them transplant humanoid brains into android bodies to grant them virtual immortality.
Mudd was detained, albeit in very comfortable surroundings, as the androids were quite happy to build replicas of any person he wanted, and provide him with any wish he could want (except freedom). When the androids attempted to abduct the USS Enterprise, the crew was able to escape by discovering the weakness of these androids; their minds were so highly logical that by intentionally acting as illogically and unpredictably as possible, the confused androids would be overloaded and incapacitated. (TOS: "I, Mudd")
They had placed their minds in spheres, becoming beings of pure energy. The android bodies would have given them mobility and allow them to leave their planet. They borrowed Human bodies to build the androids.
The plan failed when Henoch, enamored with the return of physical sensation, tried to destroy Sargon and keep possession of his host, Spock. Although Henoch's plan was foiled, Sargon and Thalassa ultimately did not use the android bodies, as they decided they did not have the discipline to use their mental powers in the physical realm. (TOS: "Return to Tomorrow")