Revealing mistake: When DiNozzo is watching the ship through the binoculars at the beginning, the film is run in reverse. The sailor smoking on the deck is the giveaway, as the smoke he's blowing is going into his mouth. (00:00:15)
Mind Games - S3-E3
Revealing mistake: When O'Neill starts taking Polaroid photos of Cassidy in the barn, Cassidy's blouse is properly buttoned up, but the second photo O'Neill takes shows Cassidy's blouse is being held together with a large safety pin, then the buttons are intact again. (00:39:10)
Untouchable - S3-E20
Revealing mistake: When the Lieutenant is explaining how her gun was in the victim's house, the camera pans behind Gibbs. Pay close attention and you can see a very faint shadow move across his back. Since we see there is nothing behind him on numerous occasions, it can only be part of the film crew. (00:18:20)
Untouchable - S3-E20
Revealing mistake: When Tony is winding the cat up in the carry basket, we see a side shot when the cat "attacks" him. However looking through the side of the cage, you can see the cat is nowhere in sight and therefore unable to attack Tony. (00:07:50)
Revealing mistake: The shot when Gibbs shows up to the scene, as Ducky examines the "deceased" girl, you can see a pulse in her neck. (00:07:00)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.