Mind Games - S3-E3
Continuity mistake: When the team are talking about Gibb's personal life, Tony's grip on his cup changes instantly. (00:12:30)
Mind Games - S3-E3
Visible crew/equipment: While Gibbs and Tony are in the car chasing after Briggs, Gibbs is on his cell with McGee getting location updates, and just as Gibbs asks, "How far ahead is he?" the camera is visible behind Gibbs and Tony, by the back seat. (00:37:55)
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)
Answer: I hadn't seen the backdoor pilots yet but while it wasn't explicitly stated, at least onscreen, I heard somewhere Vivian got either fired from NCIS due to jeopardizing a case, got resigned from the agency, or transferred to the FBI.
Raykvega423