In the Dark - S4-E22
Revealing mistake: When Tony is telling Gibbs & Ducky that Abby got a hit on the dead sailor's fingerprints, Gibbs takes the file from Tony; the camera shows the file, which appears to be a legitimate profile sheet, but in the comments section, is the script that Tony just read aloud. (00:07:36)
Visible crew/equipment: When Roger's holding the twins over the railing, Cindy grabs Maura, but Roger drops Vivian, and just as he lets the little girl fall we can see both hands of a crew member at the bottom of the screen.