You know, it's funny how often random "bit"/"side" characters grow in my mind after I finish writing the scenes they're initially involved in. They're only supposed to play a small roll, then be out of the story, but I end up giving them more personality as I write them, which is a good thing sure, but then I sometimes end up wanting to create a bit more backstory for them and tie them back in to other characters in the story in ways I didn't initially intend. Or just generally do more for them. Sometimes it really surprises me when this happens, too. 

As an example, in The Cult of the Crimson Isles, the Order group that originally took Lykou and Kuna up the mountain were supposed to mostly remain just throwaway bit characters, aside from Kalei. But I ended up making notes about not just their personalities, but also tidbits about their background, motives, etc. beyond just what was shown in the parts they showed up. And even now after they've largely been out of the story for a bit, I keep finding ways to tie them back into it. Even toying with the idea of Koa having more ties to Kalei's past than I initially planned right now.