When George and Alex are in the elevator prepping for surgery on the gunshot victim we see Alex and George both put on surgical gowns and gloves. Yet, when George removes the bandage from the wound, we see Alex look up at George and Alex is suddenly not wearing either the gown or the gloves. The next time we see Alex, he is once again in a surgical gown and wearing gloves.
In 'Bring the Pain', when Alex and George are in the elevator waiting for Burke to come back, you briefly see the opening to the lift dressed with the blue paper and two nurses in the background. When the camera pans back up a few moments later, the nurses are still there but the papered up opening is not. Nor is it there when Burke finally does reappear with what they need for the open-heart surgery.
After Derek's surgery, Meredith goes to him and asks him to choose her over Addison. When she enters the room, we can see Derek taking off his mask and on the next shot he takes it off again.
When Burke steps onto the elevator Miranda declines his offer to scrub in on the GSW, and just as Miranda admits to having a "date" that evening, a T-mark can be seen on the floor in front of Burke.