The Klingon species was named for Lt. Wilbur Clingan, who served on the LAPD with Gene Roddenberry.
The Vulcan Nerve Pinch was invented by Leonard Nimoy as a way for Spock to overpower opponents without having to resort to violence.
Before the series went on the air, Gene Roddenberry expressed concerns about the sound effects in Star Trek's intro. He wondered if the "swish" effect of the passing ship should be removed, since there's no sound in space. Desilu Studios polled preview audiences about it; the majority said they liked the effect because it conveyed great speed, and that the scientific inaccuracy didn't bother them. So the "swish" was allowed to remain.
Gene Roddenberry wanted "alien plants" for the planet's surface, but had trouble communicating the idea to the prop department. They sent dozens of lush, green potted specimens, all very terrestrial. A frustrated Roddenberry finally grabbed one potted tree, yanked it out of the soil and stuck it back in upside down with its bare, tangled roots exposed. "There," he grumped. "Now that's an alien plant!"
Don't know if its intentional or not? This is the only episode of Star Trek, (the Original Series) that I know of, where a person makes a sound after being stunned by a phaser. As Kirk and crew stun the group of men with pipes, listen carefully as the last one falls to the ground. He makes a "oh-ah" or groaning sound. After reviewing all the episodes prior and after. This is the only person who makes any kind of noise after being stunned. Maybe it was the parasite infecting his body that allowed him to do this.
"Shore Leave" was the first of many Star Trek episodes (and movies) partially shot at Vasquez Rocks, a distinctive California desert rock formation named for a 19th Century bandit who once had a hideout there. Kirk and Finnegan's fistfight and Kirk's encounter with Ruth were both shot at Vasquez. The formation is most prominently featured in "Arena," when Kirk pushes the boulder off its peak onto the Gorn.
A perennial Star Trek extra, the tall blond Eddie Paskey played a red-shirted crewman standing in the background in virtually every Trek episode for all 3 seasons. He rarely had any lines, and was even killed off in "Obsession," but was back on duty anyhow in the following episodes and for the rest of the series.
For her Orion slave girl dance, Susan Oliver was painted green from head to toe. But every time production footage of her came back from the processing lab, no trace of her green make-up job showed on film. After three rounds of Gene Roddenberry ordering the make-up crew to "paint her greener!" it was finally deduced that the lab techs, assuming her color was a lighting error, had been re-tinting her a nice, healthy pink every time.
A constant question during the run of all the Trek series is why Klingons look so much different, from "Star Trek: The Motion Picture" on, than they did in the original series. The real reason is the movies and later TV series had a better makeup budget. However, the "Star Trek: Enterprise" episodes "Affliction" and "Divergence" provide a canon answer. Klingons acquired genetically engineered human embryos left over from Earth's Eugenic Wars and used them to augment their soldiers. It worked but created a virus that threatened to annihilate the Klingon race. Dr. Phlox and a Klingon doctor found a cure, but it resulted in all Klingons becoming far more human in appearance. Sometime between these episodes and the first Trek movie, a cure was found, returning the Klingons to their present day "ridged-head" appearance.
Actress Lee Meriwether says she was teased daily by a playful DeForest Kelley while shooting "That Which Survives." He continually pulled down the glued-on cloth rectangle that NBC insisted should conceal her navel, then squinted at her tummy and asked, "What time is it?" On the final day of filming, she got back at him. When Kelley peeled off the cloth, he broke up laughing before he could ask the question. Meriwether had glued a small, ticking clock over her navel - set to the correct time, of course.
William Shatner recalls having a "lame-brained" attack of bravado during "Shore Leave's" filming and insisting that Kirk should wrestle the tiger - without a stunt double. Gene Roddenberry finally convinced him that he was much too valuable to the show to risk his life for a stunt. Thirty years later on a Sci Fi Channel special, Shatner said, "Thank you, Gene, for preventing me from becoming a hair ball!"
Scotty's line to Spock is, "Keep your Vulcan hands off me!" But the word "Vulcan" is indistinct and unfortunately, sounds rather like a certain obscenity starting with the letter F. This resulted in several TV stations across the US censoring that part of Scott's misunderstood line with a "Bleep."