Kras

Kras was a Klingon male, descended from Klingons afflicted by the Klingon augment virus inadvertently created by Antaak in 2154. 

In 2267, Kras was sent to Capella IV to obtain permission for the Klingon Empire to mine topaline there. He supported Maab's revolt against the Teer Akaar in hopes that Maab would, in turn, award the Klingons the mining rights. Kras later betrayed Maab, and was killed by Maab's lieutenant, Keel, for his betrayal. 

Background
Kras was not named in dialog, but merely and impersonally referred to as "Klingon." However, the character's name was taken from the episode's script and end credits.

Kras was mostly played by Tige Andrews, though was also performed by Jay Jones, Andrews' stunt double. That Kirk actor William Shatner was familiar with Andrews prior to production on "Friday's Child" was instrumental in landing Andrews the part. Director Joseph Pevney recalled, "That's how he got the role [....] When the time came to cast the role in 'Friday's Child', [Shatner] asked me to 'read' Tige and see what I thought of him. And I liked his look, he had a great look, and he worked out fine, I thought." Laughing, Pevney concluded, "Tige looked like a Klingon." (The Star Trek Interview Book, p. 195) Having not only met Shatner but also enjoyed watching episodes of Star Trek: The Original Series before the producers of TOS asked him to play Kras, Andrews was very pleased to accept the role. He had no second thoughts about involving himself in a science-fiction series such as Star Trek, even though "Friday's Child" was his first science-fiction appearance on television, and his enthusiasm for the part remained. "I was very much into the role," he reflected. "I particularly remember feeling more like 'someone else' during the filmmaking. It was a fun part." (Starlog #138, p. 36)

Kras was the first Klingon character to be styled differently from all Klingons that appear in, led by Kor, as played by John Colicos. Unlike those Klingons, Kras' makeup involved no darkened skin or bushy, upswept eyebrows. This Caucasoid Klingon appearance was used again on all Klingons in – including main Klingon characters Koloth, performed by William Campbell, and Korax, portrayed by Michael Pataki – before reverting to the original makeup design in the episode.

Kras was initially planned to feature as the main Klingon in "The Trouble with Tribbles". However, Tige Andrews was unable to reprise the role because the production could not fit into his schedule, as he was busy elsewhere with something that couldn't wait. Joseph Pevney noted, "Tige would have been exceptional." (The Star Trek Interview Book, p. 195)

In Marc Okrand's tlhIngan Hol language, Kras' name is properly rendered as QaS. (The Klingon Dictionary 2nd ed., p. 58)

External link
Kras Kras