My Old Friend's New Friend - S4-E1
Corrected entry: There is a scene where Carla and Turk have just arrived by cab to the hospital. Turk and J.D. see each other and Carla tells Turk "go ahead" and he runs off leaving Carla standing in front of their luggage. A few seconds later J.D. and Turk run past each other in the hospital in front of Carla, who is now magically wearing scrubs and holding a chart.
Correction: This is to imply that they have been chasing each other around the hospital for a while, missing each other, not quite able to find each other in the same place at the same time. In this span of time they are running around like fools, Carla has already changed for work and is now on shift.
Kimberly Mason