The opening shots in Kuala Lumpur were actually shot in a back-lot car park in Canoga Park, Los Angeles.
The sequence in David Palmer's campaign headquarters was originally at the end of the sequence in the pilot to be a shock, but it ended up appearing too complex.
It was very difficult to fit lights anywhere in the Bauer house as it was a very tight space.
Both Sarah Clarke and Leslie Hope's casting was finalized the same day filming was to begin; both actresses ended up wearing their own clothes for their scenes in the pilot episode. While Teri changes her clothes before leaving home, Nina ended up wearing Clarke's own outfit for most of the remaining episodes.
The editors tried to overlap split screens to begin with, but Hopkins fought against it, and says that it was important to use the technique judiciously.
The premiere features many incidental shots of clocks, an idea that was dropped after this episode.
Car scenes were produced by actually placing cameras on vehicles as they drove, while later episodes usually resorted to studio rear projection.
The exterior of CTU is actually a record company near Barrington. It is one of Peter Levy's favourite shots.
The helicopter shot of Kim and Janet arriving at the furniture store was shot for several hours by Hopkins but much of it could not be used due to a lens issue.
Kim and Janet were originally going to a rave at Santa Monica Pier, then one at the Griffith Park Observatory, but budget constraints led to using the furniture store. Both the interior and exterior scenes were filmed at the store; no set dressing was done inside apart from repositioning some objects.
Hopkins mentions Mr. Floppy, a stuffed Dachshund he found in Kim's room, and how he later sneaked it into scenes throughout the first season.
Longer lenses were used in the pilot than in other episodes.
Recording audio in the conference room was very difficult due to the acoustics of the metal grille and bars on the wall. The Director's office was also problematic for sound.
Hopkins and Levy joke that Martin Belkin doesn't look like a villain at all, with his European accent and black clothes.
Hopkins was pressured not to have Teri Bauer smash the coffee mug due to time constraints, but he did it anyway.
Despite being assured that the furniture store sequence could depict sexuality and drug use, Fox eventually forced much of the filmed material to be cut. The dialogue between Kim and Rick was edited to avoid showing them smoking a marijuana joint. More "raunchy" scenes of Janet and Dan having sex were also removed.
Hopkins made sure to include the "magic cabinet" in Jack's office, as he foresaw that both Jack and the writers would need to have quick access to different clothes or weapons if the series were picked up.
Figuring out the sequence of Mason faking the phone call and Jack getting a tranquilizer gun was difficult.
Using the split screen effect proved helpful in editing, as shots could be cropped and resized as necessary without becoming distorted.
When it was decided later in the season that Nina Myers was actually a mole, Hopkins and the writers pored over the previous episodes to make sure that none of her previous actions blatantly contradicted her actual allegiance.
Hopkins jokes that he never gets seated next to someone as attractive as Mia Kirshner on a plane.
Each scene was specifically colored so that viewers could instantly tell which scene they were in; Palmer's hotel was golden, CTU was blue, and Kim and Janet's scenes were "monochromatic."
The Bauer house and York house scenes - as well as Vincent O'Brien's scene - were all filmed at the same house.
The camera work on the pilot felt like an extension of the aesthetic in Under Suspicion, a thriller that both Hopkins and Levy worked on - using mainly handheld cameras and focusing on authenticity rather than looking good.
Hopkins consulted an FBI friend, David Hart, to find out how someone would conceivably blow up a plane the way Mandy does. The fire extinguisher bomb and the cordite charge in the bag seam are both based on actual attempted bombings intercepted by law enforcement.
The plane door explosion was done twice as, on the first attempt, not enough debris was blowing around. The scene of the plane actually exploding was excised due to the recent September 11 attacks.
Van Nuys Boulevard was frequently used for the early episodes due its being well-lit. For some reason the roads were always wet during nighttime filming.
As Mandy is parachuting out of the plane, it appears to still be dark. However, the shot was filmed in an afternoon, and in fact was heavily edited to look darker.
It was difficult to shoot Kim Bauer's escape from the Drazens due to water issues.
Leslie Hope had never seen the episode before doing the commentary.
Scenes for 24 are barely rehearsed on the set; they are occasionally done before shooting begins but never immediately before a scene is shot.
A Serbian actor was originally cast as Victor Drazen, but it was too difficult to understand what he was saying so Dennis Hopper was cast instead.
There was supposed to be a shoot-out with Victor Drazen and Jack at the end, but they decided to go with a "Shakespearean style" massacre.
The death of Drazen was not scripted as it was shot; Jack was not going to kill him in cold blood, but would simply win in a fire-fight.
It took several stunt men over half an hour to smash the window that Jack hits before entering Drazen's compound.
Three endings were planned; one of Teri's death, one of her surviving, and one of her going to the emergency room. The main reason three endings were shot was to prevent from spoilers leaking out about what happened.
Leslie Hope expressed concern about the amnesia storyline whilst it was being filmed. The storyline was based around a life experience of Hopkins.
A scene for the final shock was shot featuring Teri Bauer with "exploded guts".
Leslie Hope cried during the filming of the final scene because of Kiefer Sutherland's acting.
Initially, Joel Surnow and the other writers intended to end the first season with Jack and his family reunited, but halfway through realized that it might be a letdown after viewers had been trained to expect the unexpected. Nevertheless, they decided to film the original ending as a "safety net," in case they later decided that killing Teri came across as too harsh.
Surnow points out how Kim comes with Jack to look for Teri in the hall, then is sent away when Jack sees the dead guard, then comes running back into the tech room where the three are reunited. The setup was inelegant and convoluted, and Surnow admits that they may have been sabotaging themselves in favor of the new ending they had devised.
Ultimately, Surnow says that Teri's death made the season feel more authentic and was a major shock to viewers, one that informed watchers that in the future they couldn't take for granted any assumption they made about where the story was going.