Daniel "Lonely Boy" Humphrey!
Momentous ONTD viewing post can be found here.
E! Online about the reveal:
So who was behind the site that spread nasty rumors and gossip and controlled our gang's lives for six years, leaving them forever nervous to check their phones every time they went off in fear that it was yet another Gossip Girl blast? Dan "Lonely Boy" Humphrey! Yes, the eternal outsider turned out to also be the insider.
So how do we learn Dan was "pulling the strings" all along? Cue flashback to Dan's first UES party, where he was invited by accident by Serena. "Once I got inside, I wasn't leaving, because that's when I saw you," Dan says, though Serena doesn't remember their first Hello Kitty-referencing encounter. Before he can confess to Serena, he decides to give his final chapter to Nate and Spectator, which reveals who Gossip Girl is.
"I wasn't born into this world, maybe I could write myself into it," Dan explains after the big reveal happens. "I might have been a joke, but at least these people were talking about me." (He also reveals that Jenny [Taylor Momsen] knew it was him!) Serena defends Dan, saying he was just as hard on himself as he was on any of them.
source
May we use this post to point out all of the ways in which it doesn't make sense/why Dan is the biggest tool in the GG universe & why it's the best thing that happened in the entire episode?
Also, Nate as Mayor... that's rich.