Hey Upper East Siders. There's nothing Gossip Girl likes more than a surprise. And The CW's casting director Michael Rapaport has a two-for-one special.

"I think the network initially pitched us Ashley Olsen and Rumer Willis for Blair and Serena," Rapaport revealed to Buzzfeed. "I love Rumer, she's grown into quite an amazing actress and person, but that, to me, was based on protecting the investment of a television show where creatively, these lesser-known girls really captured the essence of the show and carried it for six years."

Word is Rappaport had only one face in mind for playing the original UES It Girl. "Blake Lively was literally the only person I could think of for Serena," Rapaport said. "I had seen her in Accepted and at that time, there were no Lena Dunhams or Zooey Deschanels — it was all about beauty and glamour, but being approachable and Blake was the ultimate It Girl."

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And just like at Constance, poor B. was forced to cater to S., even IRL. After the golden blonde Lively was cast, Rapaport said, "From there on out, so much of the casting on Gossip Girl became about hair because Leighton Meester is naturally blonde and the way we got her the job was we dyed her hair."

As for Lil J's gothic transformation, "I certainly did not see that coming ... I don't think anybody did," Rapaport said of Jenny - and Taylor Momsen - turning into a raccoon-eyed bad girl over the course of the show's run. "We were looking for a girl who was on the brink of becoming a woman — I don't think we saw that goth side yet [because] she was still really young; she was maybe, like, 13 when we cast her. Again, I don't think anyone had met her in person and everything was fine as far as I knew and then it kind of took a turn.

And though they say a leopard can't change his spots, some things do change. Olsen and Willis are pushed to the side. Meester's hair turns brown. And Momsen goes from social wannabe to rock-n-roll Queen B. Until next time. You know you love me. XOXO - Gossip Girl Dan Humphrey