- Star Trek: The Motion Picture
- Star Trek II: The Wrath of Khan
- Star Trek III: The Search for Spock
- Star Trek IV: The Voyage Home
- Star Trek V: The Final Frontier
- Star Trek VI: The Undiscovered Country
- Star Trek Generations
An Andorian belonging to one of the two male genders of the four-sexed Andorian species. In an alternate stardate 5373.4 (2269) created by the death of seven-year-old Spock in 2237, Thelin was a Starfleet officer holding the rank of commander, who served as both first officer and science officer aboard the U.S.S. Enterprise. To his great credit, Commander Thelin wished Commander Spock well, even though he knew that the restoration of the half-Vulcan science officer's familiar timeline would greatly alter Thelin's own life. Thelin's skin was a grayish-olive in color, unlike most Andorians, who have bright blue coloration. This anomaly might indicate that Thelin was of mixed Andorian and Aenar ancestry.