Doing what I want is hard

This title sounds depressing but it's not. I just like to talk about stuff in my content. A lot of the time I find myself making a concept or character I'm proud of, and I want to put it into a world or project I have, only to find it doesn't fit in its environment or lore. I wish there were easier solutions!!!! Maybe it'll be good for the archive I'm having here to fit that stuff in it, and maybe come back to them later.
To be more specific, I want to put a worm boss into a game I've been cooking up. But I'm not quite sure where it would fit.