Revealing mistake: When the smudge pot is set off, it's on the ground, smoke coming of the ends. A moment later, along with a huge cloud, if you look at the bottom of the scene, there's an area about five feet wide billowing smoke.
Revealing mistake: When Manfriedi and Johnson are in the tunnel at the beginning, the second one has a lighter going to light the way. Trouble is, there is no way that the little flame could light the area as it did. Also, the lighter couldn't have provided light to cast its own shadow inside an area that perfectly round, thereby revealing that it was lit with a light close to the camera.
Answer: The cast would have received copies of the script but with parts of the last scene omitted. They would be given the missing pages during the last days of the shoot, in which time they learn their lines, rehearse, then film the ending. Considering the time involved in filming a movie, actors do not necessarily memorize the entire script beforehand, but do so as each scene is shot. Also, it's questionable as to whether or not any of the cast did not know the ending as the movie was based on the Broadway play.
raywest ★