Oh man. So much truth here. I'm not into writing fanfics. I've been working on a screenplay idea on and off for the past few months. It takes place in New York and I've found myself using slang from that region from time to time and it's gotten progressively worse. I've even had another manager at my store from NY comment on my sudden usage of it. If I ever did get into pony fanfic, I'm pretty sure I'd end up using everypony/anypony/somepony a few times and let it slip out.