When Gossip Girl premiered on The CW in 2007, Blake Lively, Chace Crawford, Leighton Meester and Ed Westwick became overnight sensations.

The cast joined executive producers Josh Schwartz and Stephanie Savage to celebrate the show's 100th episode on November 19 at Cipriani in New York City, and only Us Weekly has an inside look at the star-studded soiree.

"I was 20 when we shot the pilot, and I just turned 21 when I went to New York City," Crawford, now 26, said on the red carpet. "Not a bad time to turn 21 and move to the city!"

Crawford's costar Lively, 24, can hardly believe she's been on the show for five seasons. "I feel so lucky that we get to be here and that we get to work here and that we get to wear these beautiful clothes," she said.

Gossip Girl's 100th episode -- which centers around Blair Waldorf's planned wedding to Prince Louis of Monaco -- airs Monday, January 30 at 8 p.m. EST on The CW.