The Traveler's species were an unnamed species of which one representative, The Traveler, was encountered by Starfleet in the 2360s. The Traveler had exceptional abilities based on their perception of time, space and thought, which allowed them with exceptional implications in propulsion, which he claimed others of his kind also possessed. (TNG: "Where No One Has Gone Before", "Time Squared", "Remember Me")
Physically, the Traveler's species had a pronounced brow line and nose bridge, as well as three large fingers on each hand.
According to The Traveler, this species had not sought contact before this time because before that, because [the Federation cultures] had been deemed uninteresting and not meriting serious attention. The Traveler himself described himself as exploring "[our] reality" (TNG: "Where No One Has Gone Before")
According to Starfleet records, the Traveler was from Tau Alpha C, a planet the inhabitants of which were known to the Enterprise computer. (TNG: "Where No One Has Gone Before") When, in 2367, Beverly Crusher tried to find him or another from his race, she directed the ship's computer to first search for inhabitants of this planet, and then try to reach the planet. (TNG: "Remember Me") A few years later, and while under a state of distress, Crusher described the Traveler as being from Tau Ceti. (TNG: "Journey's End")
With the help of Bob Justman on the Traveler's "mental makeup", actor Eric Menyuk took it upon himself to help create the alien Traveler, while falling within the guidelines of the producers wanting "someone who was definitely alien but had very human characteristics that weren't going to scare people. There was no premise." With Menyuk's input, the physical makeup was designed by Michael Westmore, "We came up with some ideas about what the character should look like. We didn't want to make him ugly, something people didn't want to look at." Once designed, the first go with the makeup application took three hours to apply and by the end of the week, Westmore had reduced that time to two hours and 15 minutes. According to Menyuk, "The makeup was so comfortable that I would forget I had it on." (Starlog, December 1988, Issue 137, p. 54)
For the Traveler's hands, special latex gloves were made, that could be simply slipped on and off, before and after takes. (Starlog, December 1988, Issue 137, p. 54) A pair of these latex hands were later sold off on the It's A Wrap! sale and auction on eBay.