The rooftop, assuming you could get up there with the stairs at all, which you usually can't on a college campus, is pretty much real: Kiddie pool, beer bongs, lots of kegs. Blair is, of course, horrified. Katie comes running up and immediately compliments Blair's necklace, and Blair tries to compliment her back and just comes up with a guilty, yucky silence, which stretches into infinity until Dan breaks the silence to go get them some beer, and tells them not to talk about high school. Everybody high-fives him and shit on the way to the keg. Egregious, but still painfully realistic.
"So was everyone at your high school totally jealous of Dan for being such a great writer?" Blair nods at Katie, then does an awesome double-take: "Dan's a writer?" Yeah, an awesome one. Maybe this year he can write a story about a girl with an eating disorder and call her Flair Smalldorf.
Georgina is quite dewy when she spots Dan, who immediately apologizes for telling her to go fuck a goat yesterday at the bookstore, and she's like, "No prob!" She keeps apologizing for all the shit she did last time, but I can't remember her doing anything bad last time. Just getting called horrible names for about fifty years and then saving all of their asses and getting Dan into NYU. Yeah, remember that? Remember how the last time they saw her, the only reason they knew she was crazy was because she called them up on the phone and was like, "That was super fun saving all your asses with no thanks or break in the abuse you guys kept handing me, and oh by the way I killed Poppy Lifton and ate of her flesh, and I'm wearing my giant psycho shades again, so watch out."
So they patch it up, I don't know how Dan does it but the agonizing apologies and back-to-normals he pulls are just Guinness level fast with these ladies, and then Georgina points out to Dan that Blair isn't looking for a second chance to smoke a beer with idiot frosch, she's looking for a way in so that she can form an army, and he has given it to her. Dan plays Vanessa in this iteration and tells G that B deserves a second chance, but her faith in B's wiles is unshakeable. "People like you here, Dan. And Blair sees that. I'm just trying to look out for you. Trust me: You're being used. Have fun!"
They keep cutting to Blair looking more and more uncomfortable at the party, and finally G just pats him on the shoulder and wanders away. Some guys hop in the kiddie pool and B stares and V drags Scott somewhere I didn't quite understand, and Dan stares at Blair and wonders if she's playing this time. I personally... Am unsure. This whole episode is about retreating to patterns, because of the facts and the figures, but it's also about being pushed back into them by the other characters' paranoia: Tell Serena she's a fuckup, and this has always been true, she'll start fucking up. Tell Blair she's being a bitch, and what do you know.