Bobby was a maintenance technician and security guard who served under the command of Captain James T. Kirk aboard the Federation starship Enterprise. While operating the transporter, James Kirk addressed Bobby as a chief. (TOS: "Charlie X")
Bobby was frequently seen working as a repair technician, responding to battle damage and normal maintenance requests. (TOS: "The Man Trap", "Mudd's Women", "The Corbomite Maneuver")
He was also responsible for security detail in several instances and was attacked by Sulu when the latter was suffering from polywater intoxication. (TOS: "The Naked Time", "Tomorrow is Yesterday", "Operation -- Annihilate!")
Bobby also wore a Sciences division jumpsuit, serving as a medical assistant at the bedside of Khan Noonien Singh. (TOS: "Space Seed")
Bobby is played by an unknown actor. The same actor can be seen in "Errand of Mercy" as a Klingon (guarding the door of Kor's office) and in a
Twilight Zone episode, "The Obsolete Man."
A post on Reddit.com
states that he is actually David Lee Ingram, (born 7 December 1941 in Los Angeles CA and died on 25 July 2012) and was never credited because he never had a SAG card.
's novelization of "Operation -- Annihilate!" refers to this character as Abrams.