Continuity mistake: When Derek talks with Mr. Chue in the rain under their umbrellas, in one shot Mr. Chue takes a big puff on his cigar. But in the next shot his face is relaxed and it is clear he didn't inhale; and then he takes the same puff again instantly anyway.
Continuity mistake: When Alex and George are trying to get out of the elevator that they are stuck in, watch the monitor screen attached to the gunshot victim. The lines on the monitor keep instantly changing appearance (from straight, to jagged, and then back, etc.), especially the middle blue line.
Continuity mistake: When Meredith, Christina and Izzy are standing by the hospital hall balcony talking, the nurse, doctor and patient extras walking and passing in the background are inconsistent from shot to shot. In addition, the position of the three ladies arms / hands on the banister keeps changing during this scene.
Continuity mistake: When Alex and George are stuck in the elevator with the doors slightly open, with the gunshot wound victim, there is blue paper lining the slight opening in the elevator doors. However this paper disappears in some shots, the reappears again.