(written from a Production point of view)
Leonard Zalman "Leo" Penn (27 August 1921 – 5 September 1998; age 77) was an actor and director from Lawrence, Massachusetts who directed the Star Trek: The Original Series first season episode "The Enemy Within". Because he ran a day over during filming, and thus ran over budget, he was not invited back to direct more episodes.
Outside Star Trek, Penn helmed well over four hundred prime-time hours on a wide variety of series, ranging from I Spy to Diagnosis Murder. In 1973, he received an Emmy for directing a two-hour episode of Columbo titled "Any Port in a Storm". Before becoming a director, he acted on stage and in a few feature films, beginning with Shame (1945). His film career had just begun when Penn (a noted union supporter) was blacklisted after refusing to testify to the House Un-American Activities Committee. He also acted in dozens of TV shows.
He is the father of actor Sean Penn, musician Michael Penn, and the late actor Chris Penn. He was also the brother-in-law of TOS guest actor Alfred Ryder. Both he and Chris appeared with William Shatner in North Beach and Rawhide, a 1975 TV movie which also featured Nicholas Guest.