Hahah the intro is definitely a bit random, but I sort of think it's a perfect choice considering where we are in the series!
There's always been a bit of an Audrey Hepburn vs. Marilyn Monroe aspect to Blair and Serena (Audrey being the classic 'lady' and Marilyn being the infamous smoke show), but then when you look at the scene where Dan ditches Marilyn for Audrey, you see that Serena's character got distracted by shiny things (a la the whole Nate, Carter, every other guy thing) and loses grip on Dan, who basically fell for Blair when Serena wasn't even looking and now that she wants him back, he's still focused on Blair.
Sorry for the rant hahaha but as goofy as it is, I always loved that scene!