Gralmek

Arne Darvin was an operative of Klingon Intelligence.

In the late 2260s, he was surgically altered to look Human. His assignment was to infiltrate Space Station K-7 and poison its shipment of grain and derail colonization of Sherman's Planet. He was revealed as a Klingon after James T. Kirk moved a tribble towards him. (TOS: "The Trouble with Tribbles")

After his failure, Darvin lost his position with Intelligence and spent a century living as a Human called Barry Waddle. After the Klingon Empire invaded the Cardassian Union in early 2372, he was trapped on Cardassia. After becoming aware of the Bajoran Orb of Time and its possibilities, he boarded the USS Defiant and used it to travel back to 2268. He attempted to take revenge on Kirk for exposing him and destroying his career by placing a bomb in a tribble. Fortunately, Benjamin Sisko and Jadzia Dax found the bomb before it exploded near Kirk and it detonated harmlessly in space. Darvin himself was captured by Worf and Odo and brought back to the 24th century. (DS9: "Trials and Tribble-ations")
 * Darvin was played by Charlie Brill.