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
Pet Shop of Horrors differ for each animal sold (although each animal's contract includes not showing it to anyone), and breaking this contract usually results in dire (and sometimes disturbing) consequences for the buyer, for which the pet shop claims no liability. Individual chapters of "Pet Shop of Horrors" are often based on these consequences, and are each written as a stand-alone story, usually introducing one or more new characters in each chapter. With the exception of the main characters and their families, it is rare for a character to carry over to a later chapter, providing the series with a very episodic nature.