The Napeans were a partially empathic species from the Alpha or Beta Quadrant. Their physical appearance was similar to most humanoids, possessing a large, leaf-shaped forehead ridge. They were biologically compatible with Humans for producing hybrid offspring. (TNG: "Eye of the Beholder")
Several individuals of Napean descent were members of Starfleet during the 2370s and 2380s, serving aboard such vessels as the USS Enterprise-D, the USS Lexington, the USS Cerritos, and the USS Rubidoux. (TNG: "Eye of the Beholder"; DS9: "Explorers"; LD: "Second Contact", "Much Ado About Boimler", et al.) Another served as a civilian member of Kasidy Yates' crew aboard the SS Xhosa. (DS9: "Family Business")
Later Napeans seen on screen all appeared to resemble Lt. Kwan, who was half-Napean and half-Human.
The Star Trek Roleplaying Game supplement Aliens (p. 113) suggests the Napeans only recently gained their empathic abilities following "a mutation by an [airborne] experiment in genetic engineering" in 2216. Their homeworld, Napea, is explained to be obsessed with conformity, having terraformed landmasses and the weather to be generally uniform across the planet. Their language, Napea, is said to be choppy and harsh-sounding.
Other Napean members of Starfleet include Kenny Thompson, the chief of security at Starfleet Academy in the video game Star Trek: Elite Force II and Jaq, a security officer aboard the USS Titan in the novel Synthesis.