Serena: "No book yet. But I found a Big Ben paperweight!"
NOLA: "Focus, girl."
Serena: "I'll keep looking, okay? I'm sure it's around here somewhere."
Diana: "A secret codebook? That was, for you, quite genius."
Serena: "It's not a compliment if it's true. Or if you say it like that. But either way, they're going to be running in circles all episode on this one."
Diana: "I would like it back, though. Would you go steal it from your friends?"
Serena: "Remind me again what this storyline is about?"
Diana: "It's a quid pro quo, Clarice. You do whatever I say, turning on your friends and alienating them like always for no real reason, and then I give you some useless crap like the outdated number for Gossip Girl's burner phone that everybody already knows anyway."
Blair comes downstairs wearing a skintight cobalt-blue Diana Payne number, adorably throwing around Diana Payne catchphrases -- "Cheers, thanks a lot. You're adorable. Spectator." -- in a tremendously enjoyable accent. While it does little to assuage one's worries that Blair will just never be a sane person again, it's much more like her long-ago craziness that she would do this, and therefore phenomenal to see.
Chuck: "[Obligatory sexual reference to seeing his one-time soulmate dressed up like his best friend's cougar and possibly his own mother.]"
Blair: "Gross. Give me the codebook."
Chuck: "What's that sliderule thing in your hand?"
Blair: "A handy tool called a cipher slide. All crazy people have them. I got mine when I was a child, desperately wishing my mother cared enough to read my diary."
Blair, immediately: "Ah, a classic [whatever] encryption. Not unbreakable, but it can take a long time, especially without software..."
Chuck: "Too bad we don't have that. Software, I mean. In 2012."
Blair: "Well, one regular set of codes all take place on Saturdays, including tonight."
Chuck: "And some of those Saturdays I remember well, because Nate was boning my mom in the room next door on them."
Blair: "So let's shake his weed-addled mind into sharing some details."