Pamelyn Ferdin
Pamelyn Ferdin  played Mary in the  first season episode .

She filmed her scenes between Thursday  and Friday  at Desilu Stage 9 and Stage 10.

Ferdin has made frequent appearances at Star Trek conventions. She is very willing to speak with attendees and sign autographs.

From 1964 through 1979, it was difficult to turn on the television or go to the movies and not find Ferdin's blonde tresses or distinctive voice. 

Ferdin was very nearly cast as Regan MacNeill in The Exorcist, based on her performance as Mary. The very similar-looking  was chosen instead as she was a relative unknown and Ferdin had already made a number of guest appearances in science fiction and suspense films and television shows.

Ferdin holds a rare place in the history of modern cinema. For 37 years, she was the only co-star to have killed a  character. In 1971's The Beguiled, she picks the mushrooms that are served to Eastwood and lead to his death by food poisoning. This 'record' was broke in 2008's , in which Eastwood's character is shot dead by a group of Asian thugs.

Ferdin's other contribution to television science fiction is Space Academy. She played Laura, a girl with ESP. Brian Tochi, another of the children of Triacus, played Teegar in that series. Space Academy spawned a sequel, Jason of Star Command, in which James Doohan (Montgomery Scott) played Commander Canarvin. 

Some of Ferdin's other film credits include Daughter of the Mind, a film version of Paul Gallico's mystery The Hand of Mary Constable. She also appeared in The Mephisto Waltz and A Tree Grows In Brooklyn.

Ferdin was the voice of Lucy Van Pelt in several of the Peanuts series of television films, and also lent her vocal talents to The Cat In The Hat, Sealab 2020 and Roman Holidays. Her latest voiceover role was on Detention in 1999.

In an example of life imitating art, Ferdin provided the voice of Fern Arable, the girl who saves and raises a runt pig in 1973's animated version of Charlotte's Web. Today, Ferdin is a leader of the Animal Defense League of Los Angeles. She married trauma surgeon Jerry Vlasak in 1986. Both Ferdin and Dr. Vlasak have been jailed numerous times for the efforts to protect animals.

External links
  – official site
  – official site
 
 

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Performers
TOS performers