Katie Cassidy has begun filming her stint on Gossip Girl! Loves it.

Leighton Meester shot scenes in New York with her Monte Carlo co-star - how random, right? - for GG on Wednesday... and she doesn't look happy about it! Of course, that's probably just the Blair in her.

Blake Lively, Leighton Meester, Ed Westwick Gossip Girl martinis cell phone brown dress sandals

Meanwhile, check out pretty boy Chace Crawford and Blake on set together. Two cute!