Green was a male Human Starfleet crewman who lived during the mid-23rd century. He served in the command division aboard the USS Enterprise under Captain James T. Kirk, during a historic five-year mission that starship undertook.
In 2266, Green, along with Crewman Sturgeon, both armed with a type 2 phaser, made up the two-thirds of the landing party that joined Captain Kirk to the surface of planet M-113 to investigate the death of Darnell, a crewman who had apparently been murdered during the visit of the previous visit to the surface. Kirk ordered Green to search for Nancy Crater, who had, in actuality, died some time before and been replaced by a creature able to hypnotically project an image of any individual it chose. Green came across this creature, and was subsequently attacked and killed when it extracted all the salt from his body, as it did to its other victims. The creature then took on the appearance of Green and returned to the ship with the rest of the landing party. Eventually, Green's body was discovered, and it was realized that the creature had infiltrated the ship. (TOS: "The Man Trap")