(written from a Production point of view)
James Gardner Brooks, Jr. (12 August 1942 – 1 December 1999; age 57), better known as Stephen Brooks, was the American actor who played Ensign Garrovick in the Star Trek: The Original Series episode "Obsession". He filmed his scenes between Monday 9 October 1967 and Monday 16 October 1967 at Desilu Stage 9 and Stage 10. He was born in Columbus, Ohio, and worked primarily in television.
Outside of Star Trek, Brooks was best known for his regular role as Special Agent Jim Rhodes on ABC's crime television series, The F.B.I., from 1965 through 1968. He was also a regular cast member on The Nurses from 1963 through 1964, The Interns (co-starring with Skip Homeier) from 1970 through 1971 and on the soap opera Days of Our Lives from 1980 through 1981. In 1971, Brooks co-starred with Star Trek III: The Search for Spock actor Robert Hooks in an unsold television pilot entitled Two for the Money.
In addition, Brooks made guest appearances on such programs as The Defenders (alongside Lou Antonio), Slattery's People (directed by Robert Gist), Twelve O'Clock High (starring Robert Lansing), The Invaders (with Paul Comi and Diana Muldaur), and Vega$ (with John Colicos and Alex Henteloff). He also appeared in two episodes of the CBS drama series Medical Center and Barnaby Jones; the latter featured Lee Meriwether as a series regular.
Brooks' stage credits include a 1963 production of N. Rishard Nash's The Rainmaker with Star Trek: Deep Space Nine guest star Salome Jens.  Brooks was also an understudy on the 1982 Broadway production of Harold, starring John Fiedler. 
Brooks retired from acting in the 1980s. He died of a heart attack in Seattle, Washington, in 1999. He was 57 years old.