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 remembers that "When [Welles] and I forgot my lines, I improvised a little, but then I was the writer. I was allowed to." However, Welles states that "Absolutely none of it was ad-libbed [...] every word in "Little Shop" was written by Chuck Griffith, and I did ninety-eight pages of dialogue in two days." According to Nicholson, "we never did shoot the end of the scene. This movie was pre-lit. You'd go in, plug in the lights, roll the camera, and shoot. We did the take outside the office and went inside the office, plugged in, lit and rolled. Jonathan