I'm pretty sure I want one of my Agents to be a Sammie from Discworld, but I'm not sure where the other would come from. The archetype I'm going for with him is an older character, coming up on middle aged, who is legendarily unsquickable, responding to every situation with a raised eyebrow, and nothing more. I'm thinking I'll take on some of the worst fics if I actually get round to writing for the PPC, as it seems I just don't get squicked by words. Thus, it seems a useful trait for an Agent working in that field to have.

So, where do you think he should hail from?

But do you know which Department you'll be wanting your agents to work in? Because if you want to write for the DMS, reading DMS missions is more important than reading DBS ones, for you to get an idea of how things work. And I'm sure hS will jump in with a link to Crashing Down et al soon enough; it's not stuff that you absolutely need to know, but he's been writing the history of various major events, and it's interesting stuff, and generally accepted as fairly canonical since half the Board views him as some sort of minor deity.

As for changes, so long as stuff's plausible and doesn't wildly counteract what anyone else has written, you should be okay. Killing off the Sunflower Official in a mission, for example, probably wouldn't go down all that well. And if in doubt you can always ask.

That's all there is to it, really. The fluid nature of PPC canon means the only things you have to acknowledge as solid canon are the events of TOS, though a lot of people have a sort of "everything is canon" mindset. Most of the major events like the Reorganisation, CD, the Mirror Multiverse thing, or some of the Sue invasions happened long enough ago to not really be relevant. You can pretty much do whatever you want as long as it's not offensive and doesn't contradict anything specifically set in stone, especially since HQ and the PPC itself are so huge.