- You might also be looking for similarly named actress Johanna McCloy.
Joanna McCoy had attended school on Cerberus. She was there in 2260 when Cerberus experienced a crop failure and the entire population was in jeopardy of starvation; fortunately, the planet was saved by Carter Winston's philanthropy.
Joanna was created as the result of a conversation between D.C. Fontana and DeForest Kelley between the first and second seasons of The Original Series. Fontana proposed that McCoy could have an estranged son, to which Kelley replied that he thought the doctor should instead have a daughter. Consequently Joanna was added to the series bible. (Writer's Notebook: D.C. Fontana, TOS Season 2 DVD special features)
In The Making of Star Trek by Stephen E. Whitfield and Gene Roddenberry, which was written before the original series's third season had aired, Gene Roddenberry is quoted as saying "In a future story we will bring McCoy's daughter Joanna aboard. She will be a lovely girl, and Captain Kirk, of course, is going to be involved with her. Dr. McCoy is suddenly going to discover he is a father viewing Kirk from a father's perspective. An interesting and sometimes angry new McCoy-Kirk relationship will be seen."
In the original draft of "The Way to Eden", the character of Irina Galliulin was originally written to be Joanna McCoy, and to be a love interest for Captain Kirk (the episode's original title was "Joanna"), but that script was ultimately rejected. The idea of again introducing Joanna was proposed in the season four script, "The Stars of Sargasso", unfortunately the series was canceled before the script could come to fruition.
The Star Trek Concordance by Bjo Trimble adds to Joanna's biography, stating that she was twenty years old (born c. 2249) and was in training to become a nurse; and that although they write each other often, Dr. McCoy's duties aboard the USS Enterprise kept the two apart.