In 2261 Dr. Roger Korby, the renowned Federation archaeologist, set off on an expedition to Exo III. Things did not go as planned, and a garbled message was received saying that Korby had been injured and was in danger of dying in the freezing environment on Exo III. He had located some nearby caves and was planning to try and take shelter there. Nothing more was heard from him.1 Assessing his chances of survival as very low, the Federation did not dispatch a rescue mission; it was not until the USS Enterprise entered the area on a routine exploration mission five years later that any follow up was possible.
Captain Kirk beamed down to the cave formations Korby had located, and was amazed to find him not only alive, but thriving in an underground complex of alien manufacture, and accompanied by several assistants. Korby revealed that his assistants were in fact androids; an alien civilisation which had lived on Exo III in the distant past had developed the ability to create utterly lifelike androids to any physical design in a matter of seconds. Korby planned to introduce the technology to the Federation gradually so as to avoid social upheavals. When Captain Kirk declined to participate in this project, Korby built and android replica of him and attempted to hijack the Enterprise with it.
The duplication process involved placing the subject into one part of a large machine, with a partly-formed android body in another part. The machine would scan the subject and modify the android to match every exterior detail of him or her. Brain patterns, memories and abilities would then be duplicated. Korby even claimed that the process could be taken a step further - the actual personality of the subject could be transferred whole into the copy.
Fortunately, Kirk was able to implant a subconscious racial bias in his replacement during the duplication process; this uncharacteristic behaviour alerted Commander Spock to the change once the android was on board. Meanwhile on the surface Kirk was successful in provoking emotional responses from the other androids, awakening a dormant sense of self awareness in them. Their behaviour became erratic, and even violent. During one fracas, Korby himself was injured - and it was revealed that he too was an android. The original Korby had been too badly injured to live, and had transferred his entire personality into an android body. Korby was forced to admit that the android's behaviour demonstrated that they were not in fact the perfect beings he had believed them to be, and he destroyed himself and the remaining android.1
In 2267 the Enterprise was hijacked by one of it's own crewmembers, a man who identified himself as Norman. Norman was an android, one of many which had been created on the planet "Mudd". The planet had been discovered by Harcourt Fenton Mudd, a Human trader who had had previous dealings with the Enterprise. Mudd had found highly advanced ancient technology on the planet which included machines which could build large numbers of androids quickly and easily. Determined to be of service to Mudd, the androids had refused to allow him to leave the planet. He had reached a compromise agreement where he would help them to kidnap other Humans to serve in return for his own freedom; however, once Kirk and his officers were on the planet the androids continued to allow Mudd to leave.
Kirk and his officers came to realise that the androids had difficulty dealing with any situation which they regarded as illogical. In such situations the androids would use an internal communications device to co-ordinate with a central link, the android Norman, in an attempt to resolve the problem. Kirk reasoned that if the Enterprise crew confronted many androids with illogical behaviour over a short space of time, Norman might be unable to cope with the overload. This proved to be the case, and Kirk and his crew were able to cause Norman to fail and collapse the whole android network.
In the aftermath, Kirk abandoned Mudd on the planet with a large number of androids fashioned to look like his wife - a woman Mudd detested intensely.2
In 2269 The crew of the Starship Enterprise was infected by an alien plague. Seeking a cure, the ship went to Holberg 917G, a nearby Federation planet owned by a recluse named Mr. Brack. Kirk and his landing party immediately noticed various oddities regarding Brack, such as copies of ancient documents in his handwriting. Brack confessed that he was in fact Flint, a Human who through some random mutation had been born as an immortal being who never aged. Flint had lived for thousands of years on Earth; when Humanity spread out into space he followed.
Flint found maintaining relationships with other Humans difficult - from his point of view normal Humans aged and died very rapidly, and he was desperate for a more durable form of companionship. To this end he experimented with making an android companion; after several efforts he produced Rayna Kopek, a female android who would be able to live alongside Flint for as long as needed.
Unfortunately, Captain Kirk and Rayna began to develop an romantic interest in one another. This prompted extreme jealousy from Flint, who refused to provide the Enterprise with the cure for the plague. After considerable argument on the subject, Rayna herself began to suffer malfunctions because of the intense emotions she was beginning to experience. Her artificial brain was unable to cope with the situation, and finally broke down permanently.
In the aftermath, Flint agreed to provide the cure for the plague. Enterprise continued on her way, leaving him alone on his world.3
Dr. Noonien Soong was one of the most controversial figures of the 2330s. A protégé of the great Dr. Ira Graves, he was a fierce proponent of the idea that not only was the positronic brain proposed in the fictional writings of Dr. Issac Asmiov in the 20th century a practical concept, but that it offered a great advantage over the isolinear and other computing technologies in use at the time.4
Soong's ideas were not well received; indeed, he became widely regarded as something of a joke in the Federation, gaining the nickname "often-wrong Soong". Humiliated by this treatment, Soong retired from public view and moved to the Omicron Theta colony along with his wife Juliana.4
On Omicron Theta Soong continued to work on a practical positronic brain, and finally began to make major strides in his work. He created a series of functional positronic brains of varying sophistication Unfortunately little is known about the details of his work because the colony was destroyed by the Crystalline entity in 2336.5
The earliest known example of a Soong type android is B-4. A prototype, B-4 had relatively little in the way of cognitive abilities - he functioned at the level of a Human child. Nevertheless, the creation of a practical positronic brain was an amazing accomplishment.6
Soong went on to create Lore. Lore was far more sophisticated and intelligent than B-4. Indeed, Lore's personality was indistinguishable from a normal Human, and he was at least the equal of a Human intellectually. Unfortunately, at some point Lore developed severe behavioural disorders. He began secretly communicating with the Crystalline entity, eventually leading it to the colony and prompting the attack which killed all the colonists.5
Soong's next creation was Data. Soong apparently felt that it had been a mistake to try and make an android with a completely Human personality, and with Data he deliberately introduced various limitations to set him somewhat apart; most notably, he programmed Data to be unable to use verbal contractions such as "we're" in place of "we are". It was apparently Soong's hope that a less Human-like android would be more acceptable to real Human beings.5
Physically, both B-4, Lore and Data are deliberately designed to appear non-Human. Although they are Humanoid in shape, all have distinctly golden skin and eyes. 7 The skin is remarkably similar to Human skin, complete with pores.8 They are physically far more capable than Humans; many times stronger and faster7, with no need to ingest food or water - though they do ingest semi-organic nutrient suspension in a silicone-based liquid medium from time to time in order to lubricate their biofunctions.9 They were designed to be functional males in every way, including the ability to engage in sexual acticity.8 Data's brain has a memory of 800 quadrillion bits and a processing speed of 60 trillion operations per second.10 All Soong androids are fitted with a series of small switches in their back which allow them to be shut down, either permanently or with reactivation after a desired period.5 They are heavier than water, but are equipped with flotation devices which can be used in emergencies.11
Others have attempted to pursue Soong's work, most notably Commander Bruce Maddox.10 Data himself produced a functional brain in 2366, but after a short period the brain malfunctioned and underwent total failure.12
It was believed that Soong had perished in the Omicron Theta attack, but in fact both he and his wife escaped the colony.13 He continued with his work, finally perfecting the poistronic brain. When his wife was killed, Soong transferred her personality into a positronic brain and built an android body which was indistinguishable from her own. The transfer was so complete that not even Juliana realised what had happened. With Juliana Soong finally realised his dream - he created an android so perfect that it was able to operate as a full Human, living and working an entire lifetime without anybody knowing the truth.14
The Enterprise visited a world in the Omicron Delta region in 2267; after some initial confusion it proved that the planet was a gigantic amusement park for an advanced alien species. The alien technology was capable of scanning the brain patterns of visitors and then constructing anything they desired in vast underground factories. The planet therefore allowed any fantasy to be lived out. The factories could produce both inanimate objects and Android-like recreations of Human beings.
In 2268 the Enterprise encountered the remnants of a tremendously advanced and powerful race in the form of three disembodied entities - Sargon, Thalassa and Henoch. The three requested that the Enterprise officers allow them to briefly inhabit their bodies, which would give them the time to construct android bodies which they could use thereafter. The technology involves was well ahead of Federation science at the time - enough so that the Enterprise's Chief Engineer could not even make sense of the basic operating principles.15
The bodies were never completed or made functional.15