> In these two cases, the effect on the reader might be identical, but in one essential information about the character was held back and in one it was develope

> In these two cases, the effect on the reader might be identical, but in one essential information about the character was held back and in one it was developed later. But we aren't talking about the reader. We're talking about the author. Plot reveals later in the story (that the reader experiences) have nothing to do with an author writing those things over time. If Doyle 'discovered' Watson (not created), then Watson is not copyrightable. If Doyle created Watson (which he clearly did, being the author of a fictitious character in a series of fictional novels and stories) then Doyle didn't "discover" anything, he just refined his creation.