Bruce Watson Bruce Watson was the American actor who played Crewman Green and the M - 113 creature ' s assumed form of Green in , the first episode of to air on television . The majority of Watson ' s acting roles were " expendables " – characters who were killed off within an episode . He filmed his scenes on Friday and Monday at Desilu Stage 9 , and on Wednesday at Stage 10 . Watson made his television debut in 1961 with an appearance on the sitcom " My Three Sons " . This was followed in 1962 with an episode of the adventure series " Route 66 " for which he was directed by director Robert Gist . Gist later directed Watson and actress Karen Steele in the first of a two - part episode of " The Long , Hot Summer " . The second part , directed by , also featured Watson and Steele , as well as Alfred Ryder and James B . Sikking . In 1963 , Watson appeared on the war drama " Combat ! " with K . L . Smith . In 1966 , he worked with fellow TOS guest actors Charles Maxwell and William O ' Connell on an episode of the western comedy " Pistols ' n ' Petticoats " . In 1968 , Watson guest - starred on the long - running western " Gunsmoke " in an episode with William Bramley , John Crawford , and Sandra Smith , all of whom , like Watson , appeared on TOS . In January 1969 , Watson was seen in " Dragnet 1966 " , the pilot to the " Dragnet 1967 " series that was already airing ( and on which Watson appeared in 1967 ) . TOS guest performers Vic Perrin and Elizabeth Rogers also had roles in the pilot . Later in 1969 , Watson guest - starred on the western series " Bonanza " , which had him working with Bart La Rue . In addition to the above , Watson made two separate guest appearances on at least three programs : " Adam - 12 " ( one episode with Joan Swift , another with William Boyett and Walker Edmiston ) , " The Mod Squad " ( with series regulars Tige Andrews and Clarence Williams III and fellow guest stars Lou Antonio , Rex Holman , Paul Sorensen , and Garry Walberg ) , and " Mission : Impossible " ( one episode with Anthony Zerbe , the other with the aforementioned William Boyett ) . Watson has also appeared on " Mannix " in 1972 ( with John McLiam ) and " Charlie ' s Angels " in 1981 ( directed by Kim Manners ) . The latter was his last television appearance . Watson also has a number of films to his credit . His first was the 1966 drama " This Property Is Condemned " , which was produced and distributed by Paramount Pictures . Watson then appeared in the 1971 war drama " Johnny Got His Gun " , which also featured Robert Easton , Byron Morrow , and David Soul . Watson had two films open in 1975 : the blaxploitation feature " Bucktown " , which starred Thalmus Rasulala and Fred Williamson , and the independent thriller " The Swinging Barmaids " , in which Watson played the lead role . In 1977 , Watson appeared in the made - for - TV movie " Billy : Portrait of a Street Kid " , in which s LeVar Burton played the lead role . In addition , Watson did some voice - over work for children ' s shows . He voiced D ' Artagnan in the animated " Three Musketeers " segments on " The Banana Splits Adventure Hour " during its first season ( 1968 - 69 ) . He then also provided the voice for Phineas Fogg , Jr . on the Hanna - Barbera cartoon " Cattanooga Cats " ( 1969 - 71 ) . When his acting career faltered , Watson continued doing voice - work , becoming a professional reader for audiobooks . Watson struggled with bipolar disorder throughout his life , a condition which degenerated in his final years . On 11 June 2009 , at the age of 68 , Watson committed suicide in his unfinished home on the foothills of the Manzano Mountains in New Mexico , just south of Albuquerque . He died exactly ten years after his " Star Trek " co - star , DeForest Kelley . On his blog , Watson ' s nephew , Randy , described his suicide as " an impulsive act in a fit of pain and rage . " In describing his uncle ' s talents , Randy said the following :