Duck and Cover
Duck and Cover was an informational film aimed at children that was produced by the Civil Defense Branch of the United States government in 1951. The film is about nine minutes long, and tells children what to do in the event of an atomic blast. Once the Soviet Union got the hydrogen bomb several years later, the idea of "ducking and covering" became largely irrelevant, as doing this would not be much help against a hydrogen blast. Nevertheless, the film has attained cult status and become an important cultural icon of the Cold War era. The film begins with animated footage of a character named Bert the Turtle, who is very alert and always ducks and covers when in danger. Later on, footage is shown of schoolchildren ducking and covering after an atomic flash.
In 2004, the film was selected for the National Film Registry of "culturally, historically and aesthetically significant" motion pictures.  (The film can also be viewed at this link, as it is in the public domain.)
Although Duck and Cover, as a means of surviving a nuclear blast, was of little protective value, it did serve other more useful purposes. It helped to remind viewers of the necessity to remain vigilant, not only against a nuclear attack, but against what would most likely be the sources of that attack, the Soviet Union and the global Communist movement. It must be remembered that the movie was produced while U.S. forces clashed with Communists in the Korean War. The threat of Communism was even more especially real at the time of the movie's production.