John Colicos

After Leonard Nimoy's Spock, his Star Trek (1966) and Star Trek: Deep Space Nine (1993) character, Kor, is the second longest running character to have been played by one actor in the Star Trek franchise. He made his first appearance as Kor in Errand of Mercy (1967) on March 23, 1967 and made his final appearance in the role in Once More Unto the Breach (1998) on November 11, 1998, more than 31 years later.
Colicos worked with Gene Roddenberry designing the look the Klingons have on Star Trek (1966). Budget constraints prevented the extensive makeup the Klingons were supposed to have so Colicos suggested they have a leathery Genghis Khan look, dark skin and hair.
Played the first Klingon commander ever seen, on Star Trek (1966).
In addition to his appearances as Kor on Star Trek (1966), he essayed another popular science fiction television character, the evil Count Baltar in the original incarnation of Battlestar Galactica (1978).
Pictured as the character Commander Kor on one of a set of five Canadian commemorative postage stamps celebrating the 50th anniversary of the television series Star Trek (1966), issued May 5, 2016. Price on day of issue was 85¢. Other stamps in the set honored William Shatner, Leonard Nimoy, James Doohan and DeForest Kelley.

[describing his acting philosophy] When all else fails, be enigmatic.
[on why he went back to Canada after spending twelve years in Hollywood] I was homesick, typecast and bored doing the same role over and over again.
[from a 1989 interview] I've always remained a 19th century, slightly hammy, overblown actor. I prefer gigantic parts with huge emotions to playing kitchen drama. All this realism is just tedious and boring. I'm too big for television now. I'm too big for my house. I belong on another planet somewhere. I wish there were a space shuttle going to Mars. I would take my Shakespeare and start a new company... somewhere up there.
Leading men are so cliched. They're so boring, so predictable. But when you get a really kooky, offbeat villain you can explore all kinds of devious twistings and turnings in the human mind. If you're a hero, well, they're all interchangeable. I don't think they're so interesting as these basic characters, which are the mainstay of all the shows anyway. People tend to remember the villains more than the heroes. Everybody wants to hiss and boo. It gives them a sense of superiority because they can feel, "Well, at least I'm not as bad as he is.".
Villains, like blondes, have more fun.