In 'Orion in the Sky', when Mark is leaving the hospital for the final time, his locker door opens to the left. However, in 'The Letter', when Carter is cleaning out the same locker, the door opens to the right.
Dr. Greene is with Dr. Pratt when he uses the hallway phone to call a patient's family doctor. Dr. Greene pushes the buttons for an outside line and has a conversation, however it is obvious none of the lines are lit up.