Character mistake: 23rd minute. Jack meets the female assassin in Anderson's apartment. She demands that he show his credentials. Jack says he's with CTU on a provisional basis and therefore he has no badge. The agent that came with Jack confirms that. Yet, in the 13th episode (minute 14) when he enters the sports shop with Audrey's husband, he shows his CTU badge to the owners in order to prove that he in fact is a federal agent.
Factual error: When Edgar proves that Mary-Ann Taylor framed Sarah to be the rat in CTU, he claims that she remotely took control of her computer by sending the signal over "a plain old AC power line." This is not possible, unless the computers were equipped with special hardware to separate the AC from the signal. If they were, this traffic would have been observed by James Heller's assistant.
Continuity mistake: When Jason and his wife are trying to escape from Marwan, they run through a corridor filled with water puddles. A few seconds later, one of Marwan's men goes through the same corridor to follow them, but none of the puddles had any ripples, which they should have considering the amount of water and time elapsed.
Plot hole: Dina Araz was executed at 8:57pmin the previous episode. At 9:01pm during this episode, the terrorists have already placed her body in the van, driven off with it, and abandoned it. Then someone had found the body, reported it in, and the information gotten to CTU. All in the course of four minutes. That is impossible, no matter how fast the terrorists were.
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.
Plot hole: At 01:50 am, Chloe is told to go to Sabir's house. She arrives there approximately 5 minutes later, at 01:55:45. At 01:58, Jack is told that the closest tactical team is 15 minutes away from Sabir's residence. A few moments later, Jack mentions that the tactical team is 10 minutes apart from Chloe, meaning they bothered to send the team over there even though any officer currently at CTU HQ, including Jack, could get over there a lot sooner.
Continuity mistake: In the first scene where we see Tony as a hostage, Mandy comes over to him and he has a white gag in his mouth, which is taut. Mandy says, "Is she gonna do the same for you?" and the camera cuts back to Tony, whose gag is now limp on both sides.
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)
Continuity mistake: Chloe tells Michelle that she's confirmed Marwan's identity using voice tags from McLennan Forrester, but all of the computer records at MF were wiped out a few episodes earlier by the EMP, according to both the MF employees and CTU. The fact that they didn't get any information from the company except for the printouts Jack and Paul extracted was a major plot point a few hours ago, so even if a real EMP wouldn't do this, the fact that it's stated repeatedly in the show means it should hold true within the series; Chloe suddenly having information from them an hour or so later is discontinuous, and thus a mistake.