Out of morbid curiosity (and if it's been asked before, please forgive me and tell me where to look), has anybody here ever introduced a character in order to solve a storytelling problem, possibly intended as nothing more than on offhand reference to somebody the readers don't ever actually meet ("human throwaway," as it were), only to have that character turn out to be worthy of an actual appearance and some real development, and take on a life of his or her own?
Well, it's not quite that extreme, but in Tangent Knights, I created the character of Spark just because I wanted to fill out a team that homaged the typical team composition of late '90s-early '00s Ultraman shows and needed someone to play the role of the cute young communications/tech officer. She ended up becoming an unexpectedly important and rich character in a variety of ways.