An on-set fire

In an effort to keep the environment as controlled as possible, all of the cell block scenes filmed for the picture were shot on a large set.

All of the windows were covered in opaque plastic sheets so that lamps could be placed behind them to give the illusion of sunlight.

While this sounds like a good idea, this move nearly ruined the entire film.

During a break, Frank Darabont and an extra were going to get a coffee when they noticed that a lamp had been placed a little too close to one of the plastic sheets.

The sheet then was set alight, though the pair were able to quickly put it out.

Had Frank and the extra not been there to notice the sheet, it's possible that the entire set for the movie would have been burned to the ground.