While the characters are recalling the last things they remember before being in the Cube, Geraint Wyn Davies' character, Simon, states he was in New Haven. When the screen divides into different views, the shot on the right/upper right of the screen is an alternate take from another Lions Gate film Davies had a role in, American Psycho II: All American Girl (2002). The similar shot in American Psycho II can be seen shortly after 1 hour 6 minutes into that film.
Used a similar staging method as the first film. The Cube was a single set consisting of identical panels for the walls and the floor (in some shots it was a green screen). For the previous movie, the crew clamped large lighting gels to the outer frame of the set so they could change the color scheme, but the all-white high-tech color scheme of this film simplified the lighting, and all they had to do to change the set in regards to what room they wanted to depict was to write on the walls with a grease pen and position certain props necessary to the plot. Some shots required the use of a green screen, especially when any door was opening. Some scenes used a full box to depict the room, but it was always the same set, just modified with extra panels.
The trivia items below may give away important plot points.
There is an extended ending (featured on the DVD) in which Kate is told that her total time in the cube was 6 minutes and 59 seconds. If you look at the other characters wrist watches (throughout the movie) it as always around 6:00. This works together with the number 60659 or 6:06:59.
When Colonel Maguire is killed, the effect of the wall of energy crashing into him is actually just created with a vacuum cleaner stuck on exhale (to blow his clothes around) and CGI, for the wall itself.