There was a character in my first novel whose role was supposed to simply be a bodyguard in one scene. Not a major character, not even much of a minor one, but there he went saving the protagonist’s life and the direction of the story changed. Clearly he wanted a larger role.
Normally, I would have let this pass, telling myself, ”Stick to the story of the protagonist!” But over and over again this minor character kept climbing out of the clay and daring to be something more. I finally realized he was going to have a larger role in the story whether I liked it or not. (And, yes, writing about a character in this manner sounds as funny to me now as it probably does to you...unless, of course, this has happened to you as a writer.)
This character eventually began taking over the story, even though I, the writer, argued with him:
“But this isn’t your book!”
“Yes, but I saved someone’s life; don’t I deserve one? I mean your protagonist is really a wimp right now. I saved him, remember?”
“You’re not even supposed to have a name,” I said.
“But I deserve one.”
So I gave in and called him Samson Pyne. Never, ever, ever give a minor character the first name of someone granted incredible strength by none other than God. Also, under no condition give him a last name that sounds like a tree. Roots will embed themselves into the story, his trunk will thicken with time, and before you know it there are branches and needles/leaves hogging all the light.
So what did I do? Well, I kept the name and cut, cut, cut his story out of the first book until I had a second book on my hands. I spent the better part of last year trying to work out how to give this new protagonist his own light by placing him in his own forest for a while. The protagonist of my first novel found his own strength again. (As an inside joke, I almost renamed the protagonist in my first book Paul B., but decided that would be going a little to far.)
If you find a minor character taking over your story, consider giving that character his or her own book, rather than resisting altogether. In the end, I think you’ll be a much happier and a far better writer for it.