Revealing mistake: Watch the line appear on the wall as Kelso cuts through the wall into the "Luxury Suite." The line is being cut with a round, drywall cutting bit such as would be used with a drill or Dremel tool. You can see it spinning as the cut is made. However, when Kelso has pushed down the wall and points the tool at Cox and the Janitor, he is now holding a standard reciprocating saw with a flat blade which would cut very differently than what was shown.
Revealing mistake: The third time Elliott exposes herself to a patient (this time to the dead one that Dr. Cox is about to pronounce), you can see quite plainly that she doesn't raise her scrub top enough to reveal her breasts. In fact, the shot is wide enough that if she had, her breasts would have been fully visible on camera.
Revealing mistake: When Carla and Elliot are walking through the graveyard, Elliot falls into an open grave. After she has fallen off the bottom of the screen, you can see her ankle flick up in the bottom of the picture, showing that she actually just fell down on the floor during shooting.