Invasion of the Body Snatchers, a novel by Jack Finney, and the movie starring Kevin McCarthy. The story of aliens invading earth and creating “pod people” to take over the human race was (probably) an allegory for the House Unamerican Activities that was looking for Communists in the U.S. during the 1930s-1950s.The 1956 movie was directed by Don Siegel (Escape from Alcatraz, Dirty Harry) and produced by Walter Wanger.