PPD = Post Potter Depression
The anxiety ridden period that Harry Potter fans will go through after the final movie is over. It is a mixture of happiness to have finally seen the movie and sadness that it is over and it's THE END. The length of the PPD is determined by how much of an uber fan each person is.
Symptoms may include: collecting any and all Harry Potter paraphernalia available, sleeping on Harry Potter sheets, re-reading Harry Potter books, watching over all previous Harry Potter movies, wearing clothing that make reference to Harry Potter in some way etc.
Friend 1: So we're going to see Harry Potter and the Deathly Hallows Part 2 this weekend right?
Friend 2: Absolutely! I can't wait.
Friend 1: Is your sister coming with us and I know she's a hardcore Harry fan?
Friend 2: Nope, she went last weekend and now she's in a serious PPD. She just sits in her room reading over all of the books.