There are four characters in the auditions that do not make it to the cells. The two left in the waiting room, the guy who walks out and the punk rocker girl that is afraid of drowning. They all were written into the sequel. The only one that had additional scenes, the punk rock girl, had her scene cut when the doctor scenes were cut from the film. It explains that she was not put in a cell because of her confrontation with the doctor.
The one cell was built in a garage; it was made of cement board and wood braces. There was no door, the wall hinged shut and bolted.
The actors never saw the cells before their scenes. They were led in blindfolded, placed on the mat, the wall was closed and bolted before they ever opened their eyes. When actors were on set, the crew were instructed to whisper, use hand gestures and not to speak to the actors. The only communication was between the actor and director. Actors spent hours actually locked in the cells. The crew would film 3 actors a day.
There was over one hundred hours of footage to go through by the end of filming. The first rough cut of the film was over fourteen hours long. In contrast, the original script was nine pages long.
When the contestants names are called by the casting assistant, she used the actors real names since no one had names in the script, except Marcus Wright. Then during editing music was played over the names.