(written from a Production point of view)
Leslie Parrish (born 18 March 1935; age 81) is the actress who played Lieutenant Carolyn Palamas in the Original Series episode "Who Mourns for Adonais?". Parrish was born as Marjorie Hellen, but changed her name in the late 1950s. She filmed her scenes between Thursday 1 June 1967 and Thursday 8 June 1967 at Desilu Stage 9 and Stage 10.
According to author Stephen Whitfield, Parrish, when she had to adorn the by William Ware Theiss designed titillating dress gifted to her by Apollo, was herself completely comfortable and had no qualms about wearing and moving in it, though it were "the crew and set visitors who had all the qualms". (The Making of Star Trek, p. 361)
The dress as worn by Parrish has gained somewhat of a legendary status in Star Trek-lore as being the prime example of Theiss' own "Theiss Theory of Titillation", and has been the eye-catcher in the 1992 Star Trek Smithsonian Exhibit.  When it was one year later sold as Lot 918 in the 1993 The William Ware Theiss Estate Auction, it brought in over ten times the high estimate of US$700 - $900, amply demonstrating its stature in lore.
Parrish herself has expressed immense pride in her performance in later life, "Whenever I watch it, I go right back to the whole thing again and cry my way through it. I relive it. My impression of it is that it's one piece of work that I'm very proud of. Of all the work I did, this is outstanding, because it is rooted in something which I believe so deeply." (These Are the Voyages: TOS Season Two, p. 115)
Nearly five decades after the Star Trek episode had aired, Parrish became acquainted again with it when she was invited to reminisce on her performance for the special feature "Inside the Roddenberry Vault (Part 3)" included on the 2016 Star Trek: The Original Series - The Roddenberry Vault Blu-ray Disc-set, commenting on recently rediscovered outtakes from the episode, including some featuring herself, most notably the one in which it was divulged that her character was pregnant from Apollo which had been omitted form the episode as aired. She also reiterated her beliefs in the futuristic philosophy behind Star Trek and her friendship because of them with Star Trek creator Gene Roddenberry, whom she had already met when she appeared in an episode of the by him created 1963-64 television series The Lieutenant.
Parrish played Daisie Mae in the 1959 musical Li'l Abner alongside Julie Newmar. She played the wholesome civil libertarian Jocelyn Jordan in the 1962 political psycho-drama The Manchurian Candidate, which also had work for her future fellow TOS guest actors Reggie Nalder, Whit Bissell and James Gregory. She starred alongside Robert Easton in Bill Rebane's 1975 B-movie The Giant Spider Invasion.
On television, she guest starred on Batman twice, first in 1966 alongside Charles Picerni and directed by Robert Butler, then in 1967, with Elisha Cook, Jr.. She also appeared in two episodes of The Wild Wild West, once with Michael Dunn, Bill Catching, Troy Melton and Hal Needham, and once alongside William Windom and Bob Herron, directed by Robert Sparr. Additionally, she also guest-starred in the series Follow the Sun alongside series star Gary Lockwood, having already done so when she made her The Lieutenant appearance.
She married Richard Bach, author of Jonathan Livingston Seagull in 1977. She has amassed about seventy-five television and movie credits (including a role in the film adaptation of Bach's novel). She and her (now ex-)husband lived in the San Juan Islands off Washington State.