When Dr. Kelso is leaning over the computer before talking to Laverne, he is on a MySpace page. When he turns to talk to Laverne, the page over his shoulder is a completely different MySpace page. When he walks away, the computer screen has no MySpace page, just the plain desktop.
When J.D. is talking to Turk about going to the carnival in the opening scene, first the cup and then the sports bag on the locker behind J.D. disappear.
When Dr Kelso is trying to break back into the room his gastric-bypass patient is in, the color of his scrubs keep switching from dark blue to light blue and back.
The hinges on the door are internal,there's no way Dr Kelso could have undone them.