The Infinite Vulcan

It was the actor's only involvement in the series, as he had not been hired to voice Pavel Chekov in the animated version due to budgetary limitations.

Set in the 23rd century, the series follows the adventures of Captain James T. Kirk (voiced by William Shatner) and the crew of the Starfleet starship Enterprise.

Koenig was hired to write the script after some of his work was passed from Susan Sackett to series creator Gene Roddenberry.

"The Infinite Vulcan" received a mixed reception from critics, who suggested that the writing could have been better, but others included it in lists of the best episodes of The Animated Series.

While exploring the newly discovered planet Phylos for possible Federation colonization, Lt. Sulu picks up a walking plant, called a Retlaw, and is poisoned by a stinger.

The plantlike alien beings who inhabit the planet approach the Enterprise landing party and their leader, Agmar, saves Sulu's life.

The Phylosians say they were nearly wiped out by a mild terrestrial disease that was brought to the planet by Dr. Stavos Keniclius, a Terran scientist who survived Earth's Eugenics Wars.

After reading it through, she thought it was good and passed it to Roddenberry, who agreed and asked Koenig if he was interested in writing for the animated show.

He accepted the offer, and started working on a plot involving cloning which was inspired by newspaper articles about the subject,[3][5] becoming the first actor from Star Trek to write for the franchise.

[7][8] Roddenberry was keen in particular to make use of the benefits of an animated medium, by including things which could not have been shown on a live-action series.

He later used a similar idea in "The Stranger", a Land of the Lost episode he wrote, in which Koenig introduced the character Enik.

[13] James Van Hise wrote in his book The Man Who Created Star Trek: Gene Roddenberry, that "some of the writing on the series", specifically that on "The Infinite Vulcan", "left much to be desired".