Funny thing: when Storyworld puts out a press release that you’re working on a novel, you never know who’s going to turn up. Somewhere, locked away in your brain, is a casting director. That director works to cast all the characters of your story, not just the heroine and the antagonist, or the heroine’s best friend and the villain’s sidekick. Those are the characters they’ll probably send you first, but eventually the director gets around to filling all the roles.
The key is to trust central casting. Because eventually, you’ll be typing along and a character will say, ‘Pete—thank goodness you’re here!’ and you’ll stop typing and say to yourself, ‘Pete? Who’s Pete?’ Trust yourself to know that you need him. Once he’s appeared, he’ll work himself into the story and you’ll realize he was meant to be there.
Always welcome walk-ons.