20 Things You Didn't Know About Star Trek III: The Search For Spock (1984)
1. Harve Bennett Got The Idea For Kirk Saving His Noble Self From A Fan Fic Poem
The idea that Admiral Kirk would effectively jeopardise his entire career on the off-chance that Spock could be saved was not always such a clear part of his character. Harve Bennett actually got the idea to write this into the story from a poem, written by a fan, that he spotted in a Star Trek magazine.
According to From Sawdust To Stardust: The Biography Of Deforrest Kelly, by Terry Lee Rioux, Bennett read this poem - specifically, the reference to Kirk's 'noble self' having been left behind on Genesis, and used this as a jumping-off point for the film.
Kirk, after breaking McCoy out of prison, advises the rest of the crew that he and McCoy have to go on. For McCoy, the reason is obvious - he's the one with Spock's soul. For Kirk, while it is his friend and brother who he's trying to save, this inclusion of his own noble self means that Spock is just as much a part of Kirk as his own soul. This added a far greater depth to their relationship while explaining the willingness that Kirk felt to disobey Fleet Admiral Morrow.
All of this - from fan fiction.