John Farrell Lieutenant John Farrell was a male Human Starfleet officer in the 23rd century . He served in the command division aboard the in 2266 under the command of Captain James T . Kirk , during a historic five - year mission that the starship undertook . When a group of three beautiful women were rescued from a doomed cargo vessel , Farrell was one of a number of male crewmembers who fell under the influence of their charm . When Harry Mudd , a criminal who was attempting to wive the women , hatched a plot to supply the women to three lithium miner s on planet Rigel XII in exchange for his own freedom , Magda , one of the women , manipulated Farrell into supplying her with a communicator and the frequency with which Mudd could contact the miners . He informed her that their names were Ben Childress , Gossett , and Benton , and that the head miner was Childress . ( ) Farrell was on duty at the navigator ' s station later that year , when an animalistic duplicate of Captain Kirk attempted to take command of the " Enterprise " and strand a number of crewmembers on the surface of a freezing planet and Farrell nearly believed the lie that the freezing crewmembers cannot be saved . When the other version of Kirk arrived on the bridge , Farrell expressed confusion as to which one of them was actually the captain , until science officer Spock made it clear that the one in command was not to be trusted . ( ) Farrell was manning the communications station when Kirk and others became stranded on the surface of a planet which had been devastated by a plague . He supplied the landing party with critical computer information regarding calculations being performed in an attempt to find a cure . ( ) Appendices . Background information . Farrell was played by actor Jim Goodwin . Farrell was originally conceived as a navigator to replace Dave Bailey , who appeared only in . Although Bailey was initially to have been in prior to the character of Farrell being created , Gene Roddenberry – in a memo to John D . F . Black ( dated ) – inspired the invention of the Farrell character by proposing , " " Since we have no way of knowing which show will air first , it is probably best we play safe with another Navigator under another name . " " In the final draft script of " Mudd ' s Women " ( dated ) , Farrell had the first name " Jim " ( Sulu , at one point , referred to him as " James - o " rather than , as he does in the episode , calling him " Johnny - o " ) . The same script also described Farrell as " " a super - conscious twenty - eight - year - old . . . red - haired , one of those people who fight to put out 100 percent all the time . . . which is too much sometimes . " " The fact he was referred to as twenty - eight at the time of the installment suggests he was born in 2238 . In an ultimately unused line of dialogue later in the script , Farrell himself alluded to having a girlfriend , saying , " " I ' ve got a girl back in . . . " " though he didn ' t complete the sentence . In the final draft and revised final draft script of , Farrell was placed in temporary command of the " Enterprise " by Spock , who left to answer a call for help from Geological Technician . For his appearance as Farrell in " The Enemy Within " , Jim Goodwin was assigned to work only a day , which was . Farrell was originally intended to appear in more episodes than he finally did . The character was originally in and . However , both times , he was deleted from the final draft script . In " The Naked Time " , he was replaced by Lieutenant Kevin Riley , played by Bruce Hyde . ( " " ) Conversely , Farrell ' s part in was , in the episode ' s final draft script , written for Uhura .