(written from a Production point of view)
Betty JoAnne Trimble (born 15 August 1933; age 82), universally known as Bjo Trimble (maiden name Betty JoAnne Conway) is an artist, writer, and a strong presence in Star Trek fandom. Trimble was one of the major forces behind the letter-writing campaign that saw the original series renewed for its third season. She was also the driving force behind the letter-writing campaign that urged President Ford to change the name of the first space shuttle to Enterprise. Trimble and her husband John also helped set up Lincoln Enterprises, the mail-order company run by Majel Barrett-Roddenberry.
Her only "official" work is the Star Trek Concordance, an episode guide and encyclopedia for The Original Series and The Animated Series, which began as a fandom publication, but was later published by Ballantine Books and endorsed by Paramount. Her fan works include the previously-mentioned encyclopedia and On the Good Ship Enterprise, a humorous work detailing her fifteen-year involvement with the show. Trimble has also written articles for numerous sci-fi magazines, including Starlog and the magazines of the US and UK official Trek fan clubs.
Trimble herself was part of Star Trek: The Motion Picture where she, along with hundreds of other Star Trek fans, made a brief appearance as a science division crewmember of the USS Enterprise in the recreation deck assembly scene. 
On Star Trek: Deep Space Nine, Trimble commented (in August 1999): "I feel that Gene might have come to like DS9, had he lived to see it. There might have been some changes. Majel recently said that GR would have hated the war in DS9, but frankly I am amazed that she cannot see the same theme in much of what Gene did, including his recent "discovery" of Earth: Final Conflict. The only reason there were not full battles in early Trek is lack of funds to pull it off, and lack of technology to show it. Otherwise, GR would certainly have added it; he knew what audiences liked. 
In the same interview, on other aspects of Star Trek she commented: "I don't know about Voyager; I can't see where it's going, and I don't feel GR would have liked that. I don't think he would have liked the last couple of movies; they were very far removed from the Trek Gene came up with". 
The 2009 DVD box release Star Trek: Original Motion Picture Collection featured a reunion of fan extras in the "Special Star Trek Reunion", including Trimble, David Gerrold, Christopher Doohan, Jo Ann Nolan, and Fred Bronson chatting on the same sound stage used for the rec deck scene. 
Bjo's current hobby and creative outlet is dyework.