(written from a Production point of view)
Marc Daniels (27 January 1912 – 23 April 1989; age 77), born Daniel "Danny" Marcus, was a director of many Star Trek: The Original Series episodes. Credited with a total of fourteen episodes (if counting "The Menagerie, Part I" and "The Menagerie, Part II" as a single episode), he is tied with Joseph Pevney in directing the most number of episodes from TOS. He also wrote an episode of Star Trek: The Animated Series, although he had only one other writing credit in his long television career. Daniels also wrote an undeveloped story outline, entitled "The Beast", for Star Trek: The Original Series.  His work on TOS garnered him one Hugo Award and an additional three nominations.
Earlier in his career, Daniels directed the first thirty-eight episodes of I Love Lucy, which started a long association he had with Lucille Ball and Desilu. In 1961, he directed an episode ("In the Highest Tradition") of Gene Roddenberry's The Lieutenant, starring Gary Lockwood. The episode guest starred Leonard Nimoy and Majel Barrett. In 1974, he directed a failed pilot written by Roddenberry, entitled Planet Earth, which featured Ted Cassidy, Diana Muldaur, Majel Barrett, Craig Hundley, and Patricia Smith. Robert Justman served as producer on that project.
Besides this, during his forty-one-year career as a television director, Daniels helmed episodes of such series as The Man from U.N.C.L.E., Gunsmoke, Ben Casey, Mission: Impossible, Bonanza, Hogan's Heroes, Kung Fu, and Barnaby Jones (the latter starring Lee Meriwether).
According to Robert Justman, Daniels "was a marvelous talent and a wonderful man. And what a find for Star Trek! [....] His film work was outstanding, crisp and energetic." (Inside Star Trek: The Real Story, pp. 203-204)
In 1942, Daniels married British actress Meg Mundy. The couple divorced in 1951. From 1951 until his death, Daniels was married to Emily Hosmer, who worked as a camera coordinator for I Love Lucy. Together, they had three adopted children: Amy; Polly; and David. Emily died in 2011. 
The following Hugo Award win and nominations were received by Daniels in the category "Best Dramatic Presentation":
- 1967 Hugo Award win for the episode"The Menagerie, Part I", shared with Gene Roddenberry
- 1967 Hugo Award nomination for the episode "The Naked Time", shared with John D.F. Black
- 1968 Hugo Award nomination for the episode "The Doomsday Machine", shared with Norman Spinrad
- 1968 Hugo Award nomination for the episode "Mirror, Mirror", shared with Jerome Bixby