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The film's working title was Mary Hagen. Special effects technician Wesley Anderson's first name was spelled "Weslie" in the opening credits. A July 14, 1947 Hollywood Reporter news item reported that due to pneumonia, Ronald Reagan was absent from the production from 19 June-July 14, 1947. Character actor William B. Davidson, who began performing in motion pictures in the 1910s, died a few weeks after the end of production of That Hagen Girl. Although he had worked on The Judge Steps Out, made earlier in 1947, that film was not released until 1949.