Alternate Character Interpretation: Hedwig as a secret agent reporting to an unnamed shadowy owl organization. Also Harry's diary entries, especially the first one, where a slightly unhinged Harry is friends with the spiders in his cupboard and reads them poetry.
Author Appeal: Mark's vision of Hagrid, "a mix of Henry Rollins, Frank Zappa, and Lemmy from Motorhead. Only much larger."
Friendly Enemy / Heel–Face Turn: the Buzznet commenter bradsmith, who initially expressed animosity towards Harry Potter and very slowly becomes a fan. Slightly subverted in that he said the series only won him over in the end due to the much better writing in the later books.
Hilarious in Hindsight: In his first review from Harry's point of view, he made a running gag of the fact that Harry was friends with the spiders in his cupboard. Mark himself found this hilarious in his reread, since spiders nearly kill Harry and Ron in the very next book.
More Popular Spin-off: His Harry Potter blog is way more popular than his initial Mark Reads Twilight blog.
Spoil At Your Own Risk: Never, ever, ever, EVER spoil any of the remaining Harry Potter plotline in the comments. Or Mark will destroy you. You have been warned...
We All Live in America: Early in his reviews Mark tended to write from a very narrow American perspective, making fun of certain aspects of Hogwarts like school houses, which are also part of the normal British private public school system. This was later lampshaded in his reread.
The Woobie: Oh god, multiplied by infinity. If you didn't want to grab Mark and give him the warmest, most loving hug in history, you HAVE NO SOUL.