Continuity mistake: In the scene where the CTU tactical team arrives at the 'lz', the chopper that first makes ground contact is marked "CTU-1", and offloads six federal agents in full tactical gear. Later in another shot of the same scene, you see "CTU-1" marked on a second chopper still circling in the air. It's clear this is not the same chopper as before, as we see the first "CTU-1" on the ground again moments later.
Continuity mistake: There's dialogue between Palmer and Novick in a hotel room with blinds pulled shut over the windows which leads up to Palmer asking, "Tell me again what I've been doing, Mike?" To which Novick responds, "Telling the truth." At this point the camera pans from Novick to Palmer before going into a cut-shot closeup of Palmer. Now look carefully at the background. The curtains are lit up from behind by sunlight. Keep watching. As the closeup shot pans slightly, you can see a sunny day and a building outside of an open window. This scene is supposed to take place less than an hour before midnight and with Senator Palmer hidden away from sight in order to maintain the ruse of his "death" in the explosion. (00:09:00)
Continuity mistake: Mike Novick and Senator Palmer are outside the car at Dr Ferragamo's office building when his office explodes. As they get back in the car, you can see over the shoulder of whichever gets into the rear, passenger-side. There is no one in the driver's seat, but when Palmer says, "Let's go," the car moves off immediately. (00:30:25)
Continuity mistake: When Jack is at the powerstation he checks his watch. It is 19:12:26, and it takes 1 min 57 seconds until we see the timer (yellow clock), which shows 19:13:47 and not 19:14:23 which it should be as the show is in real time. This is only a mistake if we consider agent Jack Bauer's watch as being accurate, but given how time-critical a lot of his work is, you wouldn't expect him to be casual about the time. (00:12:10)
Continuity mistake: When Agent Walker enters the building where Matobo is being held, Chloe tells her on com the stairway is to Agent Walker's left, she then immediately goes to the door to her right to enter the stairwell to let Jack Tony and Bill in from the roof.
Continuity mistake: At the very end of Episode 18, Jack knocks out Joe Prado after breaking his thumb and getting information from him. At the very beginning of Episode 19, we see Prado already being treated for his injuries, with a hand splint, and nurses checking his head, within the CTU clinic. Even if you factor in the opening recap sequence at the beginning of every episode, that means that Joe Prado regained consciousness, Jack unhooked his handcuffs, and dragged him back to CTU in three minutes or less.