Day 4: 6:00 P.M.-7:00 P.M. - S4-E12
Continuity mistake: When Driscoll leaves CTU, Secretary Heller asks Tony to call Division to request a replacement. Moments later, Heller says he still wants to call District. (00:14:00 - 00:14:40)
Day 4: 6:00 P.M.-7:00 P.M. - S4-E12
Continuity mistake: When Driscoll leaves CTU, Secretary Heller asks Tony to call Division to request a replacement. Moments later, Heller says he still wants to call District. (00:14:00 - 00:14:40)

Visible crew/equipment: When Nina's just been shot, and makes it to the barn to call CTU (around 7.10am), while she's speaking on the phone there's a cameraman visible on the right hand side (DVD). (00:12:40)
Andre Drazen: If Plan A fails you go to Plan B, not Plan A recycled.
Question: Did the actress who plays Nina know the entire time that she was supposed to be bad, or was this written into the show mid-season?
Chosen answer: Nobody knew, not even the writers, until at least halfway through the season when they were writing the end. They wanted to keep all options open.
Nick N.