Your writing sample is a sample of your writing, in one form or another, it doesn't have to be a sporking, and it doesn't have to be a PPC story or have your agents.

You are welcome to claim badfics ahead of time for missions or sporking if you like.

Permission piece, as DS said, cannot be a mission.

From what I've sponged up lurking about and poking my head into permission requests, a writing sample's only real purpose is to make sure that you have a good grasp of English, grammar, spelling, and proofreading/beta'ing.

Some form of spork would be fine, but you should not use a PPC mission for your writing sample.

Basically, they can be anything but an actual mission or other continuity-affecting story. An introductory piece with one's agents is pretty common, and it is useful to give us an idea of what they're like as characters. It could also be a completely unrelated original piece, or fanfic, or whatever else, though. We're really not picky; we just want to know that you can write decently, that your agents aren't Sues, and that you aren't going to try to overhaul/destroy/"fix" the organization. {= )

Tacking on questions is fine, by the way. Feel free to add more if you've got 'em.

~Neshomeh