Side Character (Properly this time)

I keep seeing scenarios where a side character in someone else's story gains sentience or whatever, but what happens when you don't? In this story, you really are the side character of the story. You don't take over and become sentient and make yourself the main character. You really, truly are just an extra in someone else's story. Ooh boy I sure hope this actually works. This is like the 5th attempt to get the fill-in-the-blank questions to actually work for me. Ugh. Edit: 6th attempt. Aaaaaaaaaaaaaaa. This should not be this hard.