(written from a Production point of view)
Carey Foster (born 18 December 1943; age 77) is a former actress and dancer, who appeared as a background performer in several episodes of Star Trek: The Original Series. She received no credit for her appearances, but her name was included on call sheets. 
Born Emmy Lou Parmenter, she started out in the entertainment industry as a dancer. At the age of 16, she auditioned for a part in West Side Story, directed by Robert Wise and featuring Richard Beymer and William Bramley. She was chosen at first, but eventually rejected, due to her young age (which would've required an on-set tutor and shorter work hours for her).
Her father knew Gene Roddenberry from their days serving in the United States Army Air Forces during the Second World War, and the Parmenters remained friends with Roddenberry and his wife, Eileen. This led her being cast in three episodes of Roddenberry's series The Lieutenant (starring Gary Lockwood, guest starring John Anderson, Sherry Jackson, Ricardo Montalban, Ted Knight, Vic Tayback, Gregg Palmer, John Bellah, Garrison True, and John Lindesmith, directed by James Goldstone and Vincent McEveety), and later in Star Trek. She appeared in the first pilot, "The Cage", portraying an Orion servant girl, however, her appearance ended up as a deleted scene.  She later played an Enterprise crewmember throughout the first season.
Using the pseudynom "Carey Foster", she appeared in smaller roles in films and television projects throughout the 1960s, usually as a dancer. She can be seen in a number of films starring Elvis Presley, including Kissin' Cousins (1964, with Yvonne Craig and Lance LeGault, directed by Gene Nelson) Roustabout (1964, with Marianna Hill, Lance LeGault, and K.L. Smith), Tickle Me (1965, with Lou Elias, Bob Hoy, and Loren Janes), and Harum Scarum (1965, with Michael Ansara, Theo Marcuse, and again directed by Gene Nelson), and the teenage musical comedies Pajama Party (1964), and Winter A-Go-Go (1965, with William Wellman, Jr., Julie Parrish and stunts by Roy Sickner). During this time, she was roommates with Terri Garr, who also appeared in nearly all aforementioned films.
Foster played a nightclub dancer in the 1967 thriller Point Blank (with Michael Strong, Sharon Acker, James B. Sikking, Sid Haig, Michael Bell, Jerry Catron, Chuck Hicks, and Felix Silla). She appeared in the 1968 musical Finian's Rainbow (with Vince Howard and Maurishka), and the 1969 musical Hello, Dolly! (with David Hurst, Billy Curtis, Morgan Farley, and Hubie Kerns, Sr.). In the latter year, she also worked as assistant choreographer on the Jack Benny's Birthday Special TV program (with Lucille Ball, Gail Bonney, and John Harmon).
She left the film industry in the early 1970s, after marrying and having four children: daughters Mary, Adrianne, Sean, and son Loren. She studied to become a Montessori teacher, and has been working at the Children's Montessori School in Lompoc, California in the past four decades. She also co-founded a dance school, Inspire Dance with her daughter, Sean, and served on the Board of Directors of the Santa Barbara Festival Ballet. She is known by her married name as Emmy Lou Crawford.