Trivia: In the scene were Blondie is using the radio, the message he is intercepting is about the Battle of the Bulge.
Trivia: One of the actors in the movie was Edmund Trzcinski. He was actually an American POW in a German Stalag, and wrote a play based on his experiences there. From there, the movie was made, based on the play, and he was actually cast in a role, as himself, re-creating it for the silver screen.
Trivia: Although it is difficult to tell for sure because the movie is in B&W it appears that the Commandant & guard staff are members of the Wehrmacht(regular army). Due to the extensive bombing campaign there was intense anger toward allied flyers many of whom were immediately killed upon capture; therefore POW camps containing fliers were guarded by the Luftwaffe(air force). It was felt fellow airman would be more empathic and treat the prisoners better.
Trivia: At the Christmas party, the POW singing "I Love You" is Ross Bagdasarian, who under his stage name David Seville, created Alvin and the Chipmunks.
Trivia: Charlton Heston was director Billy Wilder's original choice to play Sefton.
Trivia: Jay Lawrence's brother, Larry Storch, was one of the stars of the war TV series "F Troop."
Trivia: When Stalag 17 was pitched to William Holden, he very nearly passed on the lead role of Sefton. After more talks, he took the part, and won his only Oscar.
Trivia: According to the audio commentary on the special edition DVD, William Holden felt he didn't deserve the Best Actor Oscar awarded to him, and that it should have gone to Burt Lancaster for From Here to Eternity. Holden's wife believed that his win was just belated recognition for his Oscar-nominated performance in Sunset Boulevard.
Trivia: There are two instances where a character breaks the "Fourth Wall." This is when a character looks directly at the camera, as if addressing the audience. The first is when Harry is threatened by Animal after the horse races. The second is when Trzcinski is reading his letter and the bearded man listening to him say "I believe it...I believe it!" looks up as the scene ends.
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.
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