Day 3: 7:00 A.M.-8:00 A.M. - S3-E19
Continuity mistake: When Kim is working undercover, dressed up in Saunder's daughter's clothes, she comes out of the Ladies' toilets wearing brown trainers. As she sits down at the library computer, you see she is wearing her very high heeled shoes. A few seconds later, as she is walking between the library shelves, she is wearing brown trainers.
Day 3: 7:00 A.M.-8:00 A.M. - S3-E19
Plot hole: How did they manage to strip Jane of her clothes and get Kim out of her own and into Jane's in the very short amount of time they did it in?
Day 3: 8:00 A.M.-9:00 A.M. - S3-E20
Factual error: In the scene where Steven Saunders phones Tony Almeida to tell him Michelle Dessler has been captured, Steven tells Tony to open a "private web socket" to IP 257.211.16.5. Such an IP cannot exist, the maximum value for any single number in an IP is 255, anything higher like 257 is not defined. Real websites have been mentioned in the show before such as sylviaimports.com, making this reference a bit silly. Occurs at 39:38 in the episode.
Day 3: 8:00 A.M.-9:00 A.M. - S3-E20
Continuity mistake: When Jane Saunders gets into the car to go to CTU she and Kim have switched clothes again. Though the top worn by Jane is not the same as the one she wore earlier, which Kim then used. It's similar but not identical.
Day 3: 9:00 A.M.-10:00 A.M. - S3-E21
Continuity mistake: When Tony locks down Tech One from his office, the CCTV screen he's watching shows the monitors in there displaying the "locked down" message moments before they actually change to the message in the next shot within Tech One. (00:36:40)
Day 3: 10:00 A.M.-11:00 A.M. - S3-E22
Continuity mistake: During the hostage exchange, there is a shot of the black man waiting for Jane Saunders to walk to him, in the background we can just see a man stood behind a car door. However, in the wider shots and when Saunders jumps out of his car, the man is not there.
Day 3: 11:00 A.M.-12:00 P.M. - S3-E23
Revealing mistake: When Sherry is shot, the impact is visible on her shirt, but no gunshot wounds can be seen on her skin underneath, which can be seen as she falls to the ground.
Day 3: 11:00 A.M.-12:00 P.M. - S3-E23
Visible crew/equipment: When Julie is pointing her gun at Sherry, to her rear in the top right part of the screen there is a black shiny wall panel. On this panel you can see man's reflection, who appears to be wearing headphones. His reflection is in the shot for several seconds.
Day 3: 11:00 A.M.-12:00 P.M. - S3-E23
Continuity mistake: In the scene where Wayne and Fox are in Sherry's house searching for the pill container, right before Sherry asks, "What's going on here?" Wayne is seen wearing latex gloves. The camera then cuts to Sherry. When it cuts back to Wayne, his gloves have magically disappeared.
Day 3: 12:00 P.M.-1:00 P.M. - S3-E24
Continuity mistake: In the teachers' lounge Jack tells Chase that the second floor is cleared. When he doesn't get an answer he realises something is wrong and runs down to the floor Chase is searching. After he's cut Chase's hand off he runs out into the hallway and into the lounge which is suddenly on the same floor Chase was on.
Day 3: 12:00 P.M.-1:00 P.M. - S3-E24
Factual error: Chase gets into surgery way too quickly. Considering the time it would take for the paramedics to reach him, stabilise him, pack his hand in ice and bring him to the ER, and then for the doctors to get him ready for surgery, sedate him and actually start operating. There is no way they would have been able to do that in the amount of time they did.
Day 3: 12:00 P.M.-1:00 P.M. - S3-E24
Character mistake: Michelle tells the director that the target car is light blue. However, Chloe informs Jack that it is light green, which is the color of the car shown in the chase scene.
Day 4: 8:00 A.M.-9:00 A.M. - S4-E2
Continuity mistake: When Agent Lobell tries to stop a car from leaving the train station, the terrorist in the car shoots at him through a window, shattering it. When the camera cuts to a shot of Lobell falling to the ground, the window in the car is gone, but no fragments of it are on the car or the ground under it.
Day 4: 11:00 A.M.-12:00 P.M. - S4-E5
Plot hole: Jack's CTU-car arrives only 1 min 20 seconds later after he has asked for it. Remember the time he needed from the store to the roadblock in the previous episode. The CTU-car has to be K.I.T.T. with a enormous turbo boost. (00:04:20 - 00:05:40)
Day 4: 11:00 A.M.-12:00 P.M. - S4-E5
Continuity mistake: Debbie's gunshot wound travels up from her navel to right under her thorax within 40 seconds. (00:15:00 - 00:15:40)
Day 4: 11:00 A.M.-12:00 P.M. - S4-E5
Continuity mistake: When the cop in the car reaches to his microphone, his right hand is empty. When he types into the keyboard one second later, he is suddenly holding a pen between his fingers. (00:22:05)
Day 4: 12:00 P.M.-1:00 P.M. - S4-E6
Continuity mistake: Day Four: 12:00 PM - 1:00 PM. When Tariq and Behrooz are shown in split-screen digging Debbie's grave right after the commercial break (12:54:10 by the show's clock), Tariq's white t-shirt is covered in dirt. When the shot goes back to them a minute or so later, Tariq's t-shirt is much cleaner.
Day 4: 12:00 P.M.-1:00 P.M. - S4-E6
Revealing mistake: During the rescue, a few shots after SecDef Heller announces to Jack that he's also out of ammo, you see a shot of the bullet-riddled car taking a few more bullets. The new bullet holes obviously fade in.
Day 4: 1:00 P.M.-2:00 P.M. - S4-E7
Continuity mistake: When we first see the map of the powerplants that are successfully shut down (green) all the plants in Minnesota are green. Towards the end, however, one of them is shown flashing red, meaning it has not been shut down.
Day 4: 2:00 P.M.-3:00 P.M. - S4-E8
Continuity mistake: When James phones Jack, who is at Tony's house with Audrey, Jack says they are at "21408, Kipling, North Hollywood". Later, when Secret Service arrives to pick up Audrey, Jack walks outside the house, where we see the house number is actually 21048. The same can be seen earlier when Tony, Audrey and Jack first arrive at the house, but not as close-up. (00:25:05 - 00:30:05)
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.