Darleen Roddenberry
Darleen Anita Roddenberry-Bacha  portrayed a blonde girl in the  first season episode . She received no credit for her appearance and was brought into the episode by her father, Star Trek creator Gene Roddenberry.

Young Darleen, with her younger sister Dawn, shot her scenes from Thursday  through Friday , with an additional day on Monday , under the supervision of a social worker. (These Are the Voyages: TOS Season One, 2013, p. 258)

Life outside Star Trek 
Roddenberry and her sister Dawn are from her father's first marriage to Eileen Anita Rexroat, after whom she was partially named.  She had a half-brother, Eugene "Rod" Roddenberry, Jr. from her father's second marriage to Majel Barrett. 

In the 1980s, she was a Reno, Nevada real estate agent, during which she became acquainted with Richard C. Datin, Jr., the very first Star Trek studio model-maker. With Datin, she was involved in that era with some social benefit events. (The Enterprise NCC 1701 and The Model Maker, p. 104)

She passed away on October 29, 1995, at the age of 47, due to head injuries from a car accident. She was survived by her fourth husband  and two children from her previous marriages.

External link 
 

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Performers
TOS performers