Parody

Parody is a literary genre whose objective is to mock its subject by retelling it in a way that plays up its shortcomings in a humorous way. It is sometimes considered to be a form of satire, but it depends on who you ask; the two are very similar, and variance in their definitions causes them to overlap more or less depending on which ones you use. The main difference is that satire indirectly makes fun of its subject, which is usually something broad like society or a type of person, whereas parody points a very clear finger at its subject, which is usually a specific work, event, or individual.

Counterintuitive though it may be, the best parodies tend to be founded in love for the subject material. For instance, the guys who wrote Bored of the Rings had the utmost love and respect for J.R.R. Tolkien. That element of irony is partly why it's so funny. Parodies founded in hate tend not to be funny, since they often devolve into simply bashing the work.

Parody and the PPC
PPC missions are parodies of the specific fanfictions being sporked. (This is why they're sort of pseudo-legal.) They may also satirize bad writing, or facets thereof, in general. Missions tend to walk a fine line between love and hate, since PPCers on the whole love fanfiction in general, and definitely love the canons involved, but despise what the bad fics do to said canons. PPCers are encouraged to focus on finding the humor in the bad writing, and are strongly discouraged from bashing badfic authors.