Don't you love it when you're thinking about a scene and you start asking yourself how all roads led to this particular scene. You ask yourself, what is it that lurks in this character's past that has brought them to this point in their lives. And as you let your thoughts wander, all these little flashes of scenes and characters pop into your mind. You think, my, my, my, I never expected that from you. And in return, they give you a 'wait til you see what else I'm hiding' look.
What's even better is when you get a scene and although it is completely disconnected from what you've been writing, you write it anyway because you can't pass up that delicious twinkle deep in the mc's eye. Several scenes later, you have an aha moment that links everything together. You sit back, in need of a cigarette, at how beautifully these things have all joined together.
These are the moments that make all writing aggravations and struggles disappear into oblivion. Sigh, gotta love it.