Talosians were once a technologically advanced culture but a nuclear holocaust left their planet virtually uninhabitable and killed most of the species. The survivors of the nuclear war congregated in underground dwellings, where they became dependent on their mental ability to create stunningly real illusions, an ability that had been developed by their ancestors. As their mental powers grew, they lost the ability to use the technology left behind by their ancestors. The Talosians found that life using illusion was addictive, almost like a Human developing a physical and psychological dependence on narcotics. They became bored with the content of the illusions which they had. Their dependence upon these illusions for mental stimuli caused the Talosians to begin capturing space travelers to use as the living basis for their illusions.
In 2236, the SS Columbia, carrying members of the American Continent Institute from Earth, crashed on Talos IV. All aboard were killed, save for one Human; a badly-injured female named Vina. The Talosians repaired her injuries, but their work left her disfigured, as the Talosians were unfamiliar with Human anatomy. Using their powers of illusion, Vina could live as if she was uninjured and was made to appear abnormally beautiful.
In 2254, the Talosians captured USS Enterprise Captain Christopher Pike and attempted to use him to rebuild their civilization. The Talosians hoped that Pike would be attracted to Vina and would wish to remain on Talos IV. However, after assimilating the records of the Enterprise, the Talosians learned that Humans have a "unique hatred of captivity;" even when made as pleasant as possible, Humans prefer death. This made Humans unsuitable to the Talosians for breeding stock, and Pike and his crew were released.
The Talosians refused Pike's offer of trade and mutual understanding, claiming that Humans would use their powers of illusion to their own destruction. After Vina's true appearance was revealed, she was given back not only her illusion of beauty, but an illusory Pike to keep her company. (TOS: "The Cage")
This same compassion was again shown thirteen years later, as Pike's former science officer, Commander Spock, collaborated with the Talosians (defying Starfleet general orders and illegally taking command of the Enterprise) and brought Pike, himself a prisoner of his own body after an accident involving delta rays, back to Talos IV so that he could live out the rest of his life virtually free from his useless body. (TOS: "The Menagerie, Part I", "The Menagerie, Part II")
The Talosians were the first aliens encountered on Star Trek, appearing in the earliest TOS production, "The Cage". (While Spock was the first non-Human featured, his species is not mentioned in that episode.)
The Talosians were originally written as being a crab-like species. The story outline for "The Cage" (as reprinted in The Making of Star Trek, pp. 47-65) commonly refers to them as "crab-creatures" and says of the aliens, "Although in no way human, they are obviously intelligent and have digital capabilities via six multiclawed arms and legs." The outline also dictates that, among their own kind, the Talosians were to have used "claw-snap and clatter for speech" and were originally intended to have not only claws but also an "external armor-skeleton" that made similar noises. The aliens were not imagined as being capable of speech, other than the communication of their clattering claws; the commanding officer of the Enterprise (at that time, known as Captain Robert April) instead understood the aliens by translating their noises via his "telecommunicator" (a device that later developed into both the common communicator and the universal translator). Also, the aliens' mode of moving was referred to as "scuttling." (The Making of Star Trek, pp. 48-49, 58)
In the second revised final draft script of "The Cage", the Talosians are introduced as "small, slim, pale human-like creatures with large elongated heads, suggesting huge and powerful brains. They wear shimmering metallic garb." In dialog that was scripted for "The Cage" but was not included in the final version of that episode (nor any other installment), Vina says of the Talosians, "Since their minds can reach anywhere, most of them are like cocoons or larvae now. They just sit and let the thought records or some specimen live for them. Some of them hardly move, except to take that blue protein once a day." This "blue protein" is a reference to the Talosians' "nourishing protein complex."
The producers and Gene Roddenberry decided to cast the Talosian roles as females and then dub male voices over the footage. In a 1988 interview, director Robert Butler uncertainly recalled that this idea "might have been" his. He went on to say, "When I saw the characters in the script I thought it would be interesting to get a difference, and one easy difference is to cast women just because of their size and grace, and then add voice-overs later. Therefore you get an oddness, an antisexuality that certainly might be more the case in other galactic cultures than our own, and I think that might have been my notion. But at the same time I remember that when I mentioned it to Gene he had had a similar feeling that we should go bizarre, so there was not much discussion if it was my idea. If I said, 'Hey, let's do that,' he might have said, 'Yeah, I get it, it's a good idea,' or vice versa." (The Star Trek Interview Book, p. 97) The idea of casting women, with their lighter builds, appealed to Roddenberry because he thought it might give the impression that the Talosians had let their bodies atrophy in favor of higher brain development. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD) Thus, Roddenberry searched Hollywood for diminutive actresses who had faces that he deemed to be interesting. (The Star Trek Compendium, 4th ed., p. 15) A similar casting trick was used again much later, with the Sphere Builders in Star Trek: Enterprise. The same trick was also used in another of Gene Roddenberry's (posthumous) TV series, Earth: Final Conflict, wherein the Taelons (a species that, coincidentally, bear a striking resemblance to the Talosians) were all played by female actors.
The design of the Talosians additionally incorporated headpieces that – complete with their bulging veins and small, round ears – were created by craftsman Wah Chang and were blended into the actresses' own facial features by Fred Phillips and his makeup staff. (The Star Trek Compendium, 4th ed., p. 15) Chang's work on the Talosian head prosthetics also included the throbbing quality of veins, but this effect can only be seen on The Keeper's head. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD) Meg Wyllie, the actress who played The Keeper, later remembered the makeup required; "The base was an old-fashioned rubber bathing cap–the type with a chin strap. Above, or rather upon the cap, a rubber substance was placed. When that was set, the cap was removed, placed on a form and the technical special effects people finished the skull–placing the blood vessels and covering them. The makeup was not comfortable–my ears especially suffered being so confined under the bathing cap." (Starlog issue #117, p. 52) To operate the pulsing veins on The Keeper's head, Assistant Director Robert Justman hid out of the camera's line-of-sight and squeezed a small rubber bulb that inflated and deflated the veins. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD)
A small action figure of what appears to be a Talosian can be seen on Rain Robinson's desk in the 1996 of the Star Trek: Voyager episodes "Future's End" and "Future's End, Part II". The same or a similar action figure could be found in Production Designer Richard James' office during production on Voyager. (Star Trek: Communicator issue 111, p. 54)
During the making of Star Trek: Enterprise, little consideration was given to bringing back the Talosians, despite other TOS aliens reappearing on the series. Mike Sussman recalled, "To my knowledge, no one on the writing staff was pitching Talosian stories." (User talk:Mdsussman#TOS Aliens)
The Talosians are similar in many ways to the underground mutants of the Planet of the Apes series. Both are subterranean survivors of nuclear disaster with impressive mental abilities, which include the power to create thoughts and images in the minds of others.
The Talosians of the mirror universe appeared in the short story "The Greater Good" by Margaret Wander Bonanno contained in the anthology Shards and Shadows. As in the primary universe, they had used a distress call to lure the ISS Enterprise to Talos IV with the intention of having Christopher Pike mate with Vina so as to create a race of Terran slaves. However, Pike rejected her, refusing to mate with an "insipid human female." Upon learning of the Terran Empire's fear of telepaths, the Keeper decided to release Captain Pike and use him as their eyes and ears throughout the empire. The captain would give the Talosians an early warning should the empire ever decide to attack and obliterate their planet. After assassinating Pike and assuming the captaincy of the Enterprise in 2264, James T. Kirk returned to Talos IV and ordered that its surface be leveled, annihilating the Talosians for the good of the Empire.