(covers information from an alternate timeline)
In an alternate timeline created by the death of Spock at age of seven, Commander Thelin served as the First Officer aboard the USS Enterprise under Captain James T. Kirk from the years 2264 to 2269. (TAS: "Yesteryear")
Upon learning of the damaged timeline that Kirk and Spock decide to correct, Thelin was supportive. Upon hearing that, Spock wished Thelin a long and prosperous life in whatever circumstances the corrected timeline placed him in.
|First officers of the starships Enterprise|
|Enterprise NX-01:||Tucker • T'Pol • Sato|
|USS Enterprise:||Number One • Spock • Decker • Saavik (as a trainee) • Thelin|
|USS Enterprise-D:||Riker • Shelby • Data • Worf|
|ISS Enterprise NX-01:||Archer|
|ISS Enterprise (NCC-1701):||Spock|
|USS Enterprise (alternate reality):||Spock • Kirk|
Thelin was voiced by James Doohan. His pale complexion, compared to known Andorians, was due to the coloring practices of TAS - Andorians were sometimes grayish, and Orions were pale blue or yellowish instead of green. The script of "Yesteryear" specified that Thelin was to have blue skin.
In the Star Trek: Myriad Universes story The Chimes at Midnight, which explores the timeline from "Yesteryear", Thelin's appearance is explained as being the result of having an Aenar parent. Thelin's full name is given as Thelin th'Valrass.
Perhaps coincidentally, in Star Trek Online the USS Kirk is commanded by an Andorian named Thelin who has similarly pale skin.