I have thought of my shaping the story as a "tweak" kind of process, and compared it to beading (my only craft apart from writing) in that you have to be prepared to take everything apart and restart with the same beads sometimes. My rl novel is much more being thwacked, though -- didn't know when I started who all the characters would be, the problems they would lface, or places they would go. In fact, I'm about a year behind sending query letters after discovering a GREAT BIG HOLE in the middle which contradicted my climax. Have just almost finished fixing it now, and yes -- THWACK! Then go back and foreshadow it -- THWACK! But that means changing the abilities of the main character -- THWACK!

Beautiful metaphor -- thanks for it. As to "stealing" your characters, stealing is a grand tradition in lit: "Good writers borrow. Great writers steal."