Bryn Harold is friends with Lily Humphrey, which is why Blair will join the rest of the cast at Eric's birthday, and Penelope gives her a little sneering FYI about Bryn Harold and then Blair interrupts her own crazy talk -- "I'm not a typical college student, I'm a self-actualized, mature-beyond-her-years-yet-still-youthful-and-dewy working woman!" -- to yell about the gifts in Penelope's hands: She never got the sticky. Which means Dan is now a drug dealer! Or at the least a tulip-buying PATSY!
Ben calls Dan, on the way to drop off the drug tulips, to tell him that Vanessa's shambled back into DUMBO and up the fire escape and into a window and out into the living room and is now annoying him to death and could Dan please come deal with her or say the necessary words to banish her away again, and Dan's like, "I am not talking to her! She transformed herself into the doppelgänger of my sister/girlfriend, the two things she always wanted to be, and they ended up driving Serena into a lake and leaving her there until the ice melted!" Ben's like, "I'm not writing all of that down."
Dan explains that he's delivering 100 tulips for a gay kid's birthday party and Ben is like, "Serena totally sold him out. I hate it when she dicks him around! Unless it's by fawning all over me in his house, where she decided I would live without notifying him first." If only Ben knew that this is the only person she ever does this to, due to her inability to ever keep it together, and that she's going to arranging his life around him for her own benefit for the rest of their time together. (And yes, I did eventually get the "Ithaca Is Gorges" joke from like a month ago.)
Eric and Serena are distraught to see Dan with the 100 tulips, and even more distraught when the see that he has fucked them up: They're purple, not pink, and their fertilizer is only good for fertilizing plants, not terrible ideas at 4 AM. So now on the one hand Dan is not a drug dealer, but on the other hand Damien is going to come and kill everybody and whatever. Dan wants to know what's going on, because he always does, and as usual Dan, you don't really actually want to know what's going on, it would only freak you out.
Party time! Blair walks in and both Dan and Serena are like, "What the fuck were you thinking?" Um, she was thinking, she "would arrive at this party, and be greeted appropriately?" Dan accuses her of abusing the sacred "I trust Dan Humphrey" card just to get him to be a drug mule, and she's like, "I wouldn't do that to you, but Penelope is a bitch and frankly her attitude could use some time behind bars." And that's the end of that part of the story, it's amazing. Dan's like, "You're not going to apologize?" No, huh uh: "Well? You're here. The party's lovely. Everything obviously turned out fine."