The Little Shop of Horrors recalled "at first they told me it was a detective movie; then, while I was flying back [to make the movie], I think they wrote a whole new movie, more in the horror genre. I think over a weekend they rewrote it." The screenplay was written under the title "The Passionate People Eater". Welles stated, "The reason that "The Little Shop of Horrors" worked is because it was a love project. It was "our" love project." The film was partially cast with stock actors that Corman had used in previous films. Writer Charles B. Griffith portrays several small roles. Griffith's
The Little Shop of Horrors was called upon to write music for Corman, Katz sold the same score as if it were new music. The score was used in a total of seven films, including "The Wasp Woman" and "Creature from the Haunted Sea". Katz explained that his music for the film was created by a music editor piecing together selections from other soundtracks that he had produced for Corman. Howard R. Cohen learned from Charles B. Griffith that when the film was being edited, "there was a point where two scenes would not cut together. It was just a visual jolt, and it didn't