Vox (the librarian hologram played by Orlando Jones) was originally written to be a robot. Steven Spielberg, however, was creating A.I. Artificial Intelligence (2001) at the same time, and had a similarly-designed robot in his own film for every version of Vox the filmmakers could conceive. Production designer Oliver Scholl came up with the idea of a hologram.
Originally scheduled for December 2001, the release was bumped to March 2002 because of a decision whether to remove a scene involving a meteor shower which crippled New York. The filmmakers were concerned that such a scene may stir memories of the terrorist attack on the World Trade Center.
Vox mentions a "Time Machine" musical and starts singing a song with the lyrics "There's a place called tomorrow...". Such a musical and such a song do not exist, although its composer Andrew Lloyd Webber most certainly does.
When Hartdegen starts to travel to the future, he watches three mannequins in a shop window and as their clothes change across the time. In The Time Machine (1960), George watches the change of clothes of a mannequin during his time travel.
The opening scene was shot at Vassar College in the fall of 2000. The students in the scene are actual students and the professors are actual professors. Several additional scenes were shot but did not make it into the film. One specific scene that was left out was shot with about 10 Vassar students and features them walking around the campus in front of the library with Guy Pierce. The scene can be viewed in the DVD extras. The students were all allowed to miss classes during the shooting and were all paid for their efforts.
"Filby" from The Time Machine (1960) appears as a florist. When Young picked out his costume, he found the same period shirt he wore in the earlier film, complete with his name written on the collar! (Source: DVD production notes)
When Vox explains Hartdegen's biography, he mentions "1869-1903" as his years of birth and death. Since then Hartdegen stands in the future, 1903 turns in the year of his missing. According with it, Hartdegen is 34 years old when he travels to the future. Guy Pearce was just one year older at the point of the movie.
When Hartdegen talks with Vox about time travel, the latter mentions three real Sci-Fi writers: Isaac Asimov, Harlan Ellison and H.G. Wells. Asimov wrote "The End of the Eternity" in 1955 about time travel and the risks of making changes to the past. Ellison wrote numerous scripts science fiction (including time travel) for TV series like The Outer Limits (1963) and Twilight Zone (1959). Wells wrote "The Time Machine" in 1894, the book upon which this movie is based.