When your watching a film of a film within a film and you dont know what layer of the film your in.
A good example of this would be Cloverfield or Suzhou River.
Where in the film you see the film from handheld camera's perspective in the film.
Guy 1: I can't tell if im in a film or not, so i chopped my hand to see if i had a robotic left arm.
Guy 2: I think your in a bad state of Filmception!