know he exists. Cast Cast adapted from the American Film Institute. Production Development and pre-production Richard Matheson's idea for the original novel was inspired by a scene in the film Let's Do It Again, where Ray Milland's character leaves an apartment with the wrong hat. It is much too large for Milland and sinks down around his head and ears. Matheson sold the rights to Universal on the condition that he write the screenplay. It was Matheson's first screenplay, a writing format he felt he adapted to quickly. Matheson's initial script followed Scott Carey already shrunken and battling a spider in his basement. His rewrite is told in flashback form: scenes of Carey and the spider are interspersed with scenes telling the story of Carey's gradual loss in height. The film was already into its second month of production before the novel was published in May 1956 by Gold Medal Books. Producer Albert Zugsmith added the word "Incredible" to Matheson's title and passed the script to Richard Alan Simmons, who removed the script's flashback structure. Matheson later discussed working with Universal, finding that the producer had a "very commercial mind" which made the script weaker in terms of character. In an interview in Cinefantastique magazine, Matheson stated he protested sharing a screen credit with Simmons. The screen credits list Matheson as the writer, while the shooting script lists both Matheson and Simmons. Pre-production was originally set to begin on April 20, 1956, but it started officially on April 24. The cast consisted of mostly unknown actors. Director Jack Arnold phoned Randy Stuart, who was a personal friend, asking if she would be interested in doing the film. Zugsmith initially wanted Dan O'Herlihy to play the role of Scott Carey. O'Herlihy had just been nominated for an Academy Award for his role in Robinson Crusoe. After reading the script, he refused to play another isolated character, not wanting to be typecast in that kind of role. Grant Williams was cast because Universal had him pegged to become a star. On April 4, 1956, Williams and Stuart were screen tested and deemed acceptable for the roles of Scott and Louise Carey. Filming On the first day of production, May 31, Universal's operating committee decided that because of the type of special photography involved in the making of the film, the publicity department would cooperate by publicizing a closed-door policy on the set.