Faran Tahir appeared previously in "Day 2: 6:00 P.M.-7:00 P.M." as the Mosque Greeter. It's possible that he was the same character. If you look closely at his profile, you can see that he was a member of Second Wave, the terrorist organization from "Day 2".
Fox decided to deviate from their normal 24 airing schedule and delay the season premiere until January 2005. This gave viewers a longer break in between seasons, but ultimately allowed the show to run without preemption for its fourth season. Fox further decided to move 24 from its usual Tuesday night time slot to Mondays, kicking off the season with a special two-night "miniseries" premiere consisting of the first four episodes airing on Sunday and Monday evenings.
As of this episode, William Devane (James Heller), Kim Raver (Audrey Raines) and Alberta Watson (Erin Driscoll) join the regular cast.
Season 4 is the first season in which the premiere episode does not feature the line "events occur in real time" in its opening.
The Season 3 DVD set contains an exclusive six-minute prequel that sets up events for the beginning of the fourth season. The first scene occurs three months after the conclusion of Day 3 and shows Driscoll firing Jack from CTU because of his drug use. The second scene takes place one year after Jack's firing and shows a terrorist sneaking across the U.S./Mexican border, and then killing his accomplices. The third and final scene occurs six hours before Day 4 begins and shows Jack and Audrey in a love scene. The prequel is available on the Region One set, but not Region Two. See "Season 4 Prequel."