Glenn Morshower, who plays Aaron Pierce, is the only actor besides Sutherland to appear in all seven seasons.
Alberta Green, who makes her first appearance in this episode, was named for actress Alberta Watson, whom series creator Joel Surnow originally wanted to play the role. Ironically, Watson played Erin Driscoll, a character that is by-the-book, much like Green is, in Season 4.
Jack's opening monologue changed subtly as the season moved on. It began, "Right now, terrorists are plotting to assassinate a presidential candidate, and my teenage daughter is missing." It then became, "...and my teenage daughter has been kidnapped," then "...my wife and daughter have been kidnapped," then, "...my wife and daughter are in danger," and finally, "...my wife and daughter have been targeted."
Co-creator Joel Surnow originally named Carlos Bernard's character "Tonio" Almeida, but Kiefer Sutherland was unable to say this name and ended up calling him "Tony" instead.
Fans have long speculated what Jack whispers to Nina in this episode. According to Kiefer Sutherland the scripted line was "I am going to hunt you down for as long as you live" but what he actually whispered was "I love you Sarah, why did you marry Xander?" Sarah is the name of the actress playing Nina and she is married to Xander Berkley who played George Mason. Apparently Sutherland whispered this to get a more interesting reaction from Nina.
Co-creators Joel Surnow and Robert Cochran have admitted to naming characters after tennis and chess players respectively, while producer Michael Loceff names characters after people from Foothill College, where he teaches.
The fabled 'bunny' who appears silhouetted in a scene in season 1 appears many times, according to this interview with Elisha Cuthbert: http://www.homunculus.com/articles/cuthbertelisha/cuthbertfhm0210.html
The main character of the show was originally going to be named Jack Barrett. The creators of the show decided they didn't like the name, and changed it to "Bauer" after Elaine Bauer, an executive at Imagine Entertainment.
Over the course of each season, Sterling Rush (head of the props department) takes an average of 10 to 12 thousand photos of sets, props and characters, in order to ensure continuity between scenes and episodes.
The house used as the Warner residence was once owned by both Bing Crosby and Andy Griffith.
Episode 19 - Series 3. The website for Sylvia Imports which David Palmer must use to provide Stephen Saunders with a list of the 42 overseas agents actually exists. On it is written: "Sylviaimports.com - A Big Thank-you from the crew of 24. Thanks for watching, we love making it for you, and yes, we did get picked up for Season 4."
We get the impression from the first few episodes that Nina is trustworthy only to find out in the last 2 episodes that she was the main mole inside CTU. It's funny though that it was in front of our eyes the whole time, by accident or design: Every time that Jack says his famous starting monologue,when he comes to the part "...and people I work with might be involved in both..." we see Jack looking at Nina.
At the end of the episode, Jack takes Kate out of CTU. When Tony tries to stop them, Jack throws him to the floor and he falls badly on his ankle. Tony spends the rest of the season on crutches. The reason for this is that Carlos Bernard, who plays Tony, broke his ankle playing basketball so the writers had to alter the script to take this into account.