The PPC is a group of people who like to write. I like to write, so why wouldn't I be interested?

We all need beta readers and grammarians to pick over our work, but it's hard to find that IRL. Go online, though, and you can meet other people who also like to write, and care about writing well.

I like to read the missions that people write, and I've gotten pretty skilled at preventing whatever I'm drinking from squirting out of my nose due to the inevitable laughter.

That's a complicated question, isn't it?
On one hand, it exists as a medium to express our displeasure at those who would corrupt our fandom with bad writing/spelling, bland OCs, Mary Sues, poor grammar, and to generally mock them as often as possible. Unlike the Official Fanfiction Academies, the PPC doesn't exist to teach writers to do better while delivering an amusing tale at the same time, it is there for the sole purpose of comedy.
On the offhand, it is capable of creating an entire world built around a simplistic concept, filled with characters that make us laugh, cry, and go 'Sweet bifurcated Darth Maul! That was awesome!' The PPC is more than just a costume, it's a culture. A culture filled with half-mad assassins/exorcists/space-time cops/reformed villains armed with lethal weapons, but a culture nonetheless.
A tale from the PPC must be funny, entertaining, immersive, and most importantly, it must be written from the heart. It's an exercise in self-expression, and a way to inform writers that what they're posting is not the best they can manage, they can always do better. I've seen so many stories with excellent premises, but are executed(both ways) so poorly it makes me cringe.

This gives me an idea. To all you agents out there, try finding a fic with a good idea at the center and nurturing that tiny breeze until it grows into a great wind that sweeps over the internet like a... like a great wind!

My time is coming. I think things, and they happen.