Immediately the muse declared -- and you must put in a fairy tale allusion in there! And while I was working on fitting that into the story, she sat in the corner playing with her blocks and announced, before I was half done -- and, oh yes, remember this character's back story? The Golden Bird he was robbed of?
It has to show up again.
Needless to say, how I don't know. One of my muse's favorite tricks is declaring things Chekhov's Guns without bothering to explain how they will appear later.