10 One-Off Star Trek Characters Who Never Left
6. Kor
Initially, John Colicos was not meant to be a recurring guest star when he took on the role of Kor. In fact, the Klingons were really a means to a cost-effective end in the episode Errand Of Mercy. They were standing in for the much more expensive Romulans, those aliens with the prohibitively expensive ears. Therefore Kor, with his dark face paint, burlap sash, and bubble-wrap belt, was a quick and easy stand-in.
Then, Colicos delivered his performance, and the producers instantly knew they wanted him back. There was an issue, however, in that he wasn't available when it came time to shoot The Day Of The Dove. He was replaced by Michael Ansara, who played Kang. Now, producers were faced with another dilemma - this actor was excellent as well. Throw in William Cambell as Koloth and there was a revolving door of excellent bit-part players.
However, it was Colicos who would eventually receive the most screentime. All three returned for Deep Space Nine's episode Blood Oath, though this would be Cambell's last appearance. Ansara would appear once more in the Voyager episode Flashback. Colicos, however, returned twice more. Once, in The Sword Of Kahless, and a second time in Once More Unto The Breach.
Despite his popularity, Colicos couldn't argue the makeup team out of giving him the ridges. That one was non-negotiable.