Earth Two natives A list of unnamed Earth Two native s . Boy creature . The boy creature was one of the Onlies that was beginning to turn into a grup . Child ren entering puberty developed the fatal form of the life prolongation project . Although it prolonged this child ' s life , as he was entering adulthood he became insane and dangerous . He encountered a landing party from the , shortly after they arrived on Earth Two . Moments after Doctor McCoy caused a tricycle in a dilapidated street to make a small noise , the creature revealed himself , maniacally rushing at McCoy while repeatedly shouting , " " Mine ! " " He was hauled off McCoy by Captain Kirk and Lieutenant Commander Spock , then assaulted three times by Kirk , before the creature finally gave up on his attack . He was saddened that someone had clearly broken the tricycle , and appealed for the members of the landing party to fix it . Though McCoy agreed to this , the creature was convinced they didn ' t actually want to help him . He then began apparently suffering some kind of seizure . Responding to Kirk saying the landing party wanted to help him , the creature frenziedly repeated the word " fibber , " until he died moments later , his right hand still clutching onto one part of the tricycle . ( ) Blonde girl . The blonde girl was a member of the Onlies . She suffered from a life prolongation project that , although it prolonged her life , would kill her when she reached puberty . ( ) Boy with brown - hair . This brown - haired boy was one of the Onlies on Miri ' s planet in 2266 . He attempted to attack Captain Kirk with a club , but was quickly disarmed and pushed away . ( ) Boys who stole communicators . These boys helped Jahn steal the communicator s from the landing party from the . ( ) Boy in army helmet . The boy in the army helmet was one of the Onlies . He lived on Miri ' s world in 2266 . He was nearly three hundred years old due to the life prolongation project which greatly extend the lifespan of an ordinary cell . The complex had a fatal flaw – it killed adults , but not before making them insane and homicidal . When a landing party from the " Enterprise " beamed down to the planet , this boy along with the other children attacked them because they feared adults . ( ) Boys in army helmets . Three boys with army helmets lived on Miri ' s planet and where in a group of Onlies led by her . They helped harass the landing party from the " Enterprise " that beamed down to the planet . They all suffered from the life prolongation project . ( ) Boy in deerstalker cap . This boy in a deerstalker cap was one of the Onlies on Miri ' s planet in 2266 . ( ) Boy in cowboy hat . This boy in a cowboy hat was one of the Onlies on Miri ' s planet in 2266 . ( ) Boy in football helmet . This boy in a football helmet was one of the Onlies on Miri ' s planet in 2266 . ( ) Boy in metal helmet . This boy in a metal helmet was one of the Onlies on Miri ' s planet in 2266 . ( ) Brunette girl . The brunette girl lived on Miri ' s planet and was hundreds of years old due to a life prolongation project . When the landing party from the " Enterprise " appeared on the planet , she and the other children attacked them . They feared adults because the life prolongation turned those who entered puberty into insane homicidal maniacs . ( ) Chubby little boy . The chubby little boy lived on Miri ' s planet and was in a group of Onlies led by Jahn . He helped harass the landing party from the " Enterprise " that beamed down to the planet . ( ) Dirty - faced girl . The dirty faced girl lived on Miri ' s planet and was in a group of Onlies led by Jahn . She suffered from the life prolongation project . ( ) Girl with hat . The girl with hat lived on Miri ' s planet and was in a group of Onlies led by Jahn . She helped harass the landing party from the " Enterprise " that beamed down to the planet . She suffered from the life prolongation project . ( ) Jahn ' s friend . Jahn ' s friend was an Only that lived on Miri ' s planet and suffered from the life prolongation project . He was Jahn ' s best friend and followed him without question . Jahn ' s friend enjoyed being the center of attention , and role - played as authority figures , including a teacher and a policeman . He was usually one of the first to suggest punishing others , and fostered a mob mentality through his chanting of " " Bonk , bonk ! " " and the like . He carried a hammer that he used to bludgeon Captain Kirk . ( ) Little blonde girl . The little blonde girl was in a group of Onlies led by Jahn . She helped harass the landing party from the " Enterprise " that beamed down to the planet . In the classroom she held onto a Krazy Kat stuffed animal . ( ) Little girl . The little girl was a member of the Onlies , a group of children suffering from the life prolongation project . James T . Kirk picked her up when trying to convince the other children to let the crew of the " Enterprise " help them . ( ) Red - haired girl . This red - haired girl was one of the Onlies on Miri ' s planet in 2266 . ( ) Redheaded boy . The redheaded boy was an Only that was entering into puberty and started to show the fatal effects of the life prolongation project that prolonged life in children , but caused insanity and homicidal tendencies before killing them . ( )