Serena and Blair often butt heads on Gossip Girl, and sometimes it even gets physical. If these photos from the Paris set are any indication, another altercation is on its way!

It's unclear what's being said between the characters, of course, and we may have to wait until September to find out. But our beloved S and B are in one of those moods:

TROUBLE BREWING: It's not clear why, but Blair and Serena appear at odds.

Click to enlarge more photos below from this Parisian scene, which looks like it ends with one of our girls one an unplanned dip in a fountain. Comments and theories welcome!

UPDATE: Sorry to burst the bubble of Chair fans who hoped this was actually Clemence Poesy clashing with Leighton, but it's definitely Blake. Here's a clearer shot of her face:

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.