Continuity mistake: When Julian sarcastically sings 'Silent Night,' he jumps up in the car and knocks the mirror on the dash upwards out of place. In the next shot it shows it back to normal and then it goes out of place again.
Continuity mistake: In the scene at the party when Blair is talking to Clay, the camera cuts away and from shot to shot, Blair's hair is slightly different, going from curly to a little less curly (wavy). Also the background lighting is slightly different as well.