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Working titles of this film were Battle of the Brain Eaters and The Keepers. According to a January 1960 Variety news item, science fiction author Robert A. Heinlein sued American International Pictures for $150,000 in damages, claiming that The Brain Eaters "copied, imitated and appropriated" his serialized novel The Puppet Masters (which was later filmed in 1994). The outcome of the suit has not been determined. Leonard Nimoy's surname was misspelled "Nemoy" in the onscreen credits.