As per the original movie's attempt to portray a living robot in the "real world", every part of Johnny and his brethren was built to have a specific, logical purpose behind them; this was originally a source of contention between the director and the prop designer, the latter of whom insisted on giving Johnny "eyes" to give the character a method of visually expressing emotion. As a result, Johnny's iconic "eyelids" were created, with the explanation that they were sun guards/camera coverings.
Many of the little tricks done by Johnny 5 on-screen (like flipping through book pages in a blink of the eye and tossing a washer into the air in a mimic of a scene from an old gangster movie he saw) were done using relatively simple, yet ingenious sleight-of-hand prop effects. For instance, the pages were flipped using an air hose, while the washer was flipped using a piece of string at both ends sideways. Not only did this save money for the producers for the actual robot and the screenplay, but they proved remarkably effective in getting just the right look needed for the scenes.
There was a script for a possible third Short Circuit movie written in 1989 and rewritten in 1990, but it was found to be unsatisfactory by the producers, and the project was subsequently scrapped. According to Variety magazine in April of 2008, Dimension Films had bought the rights to make a third Short Circuit movie, in which the plot would involve a boy from a broken family meeting and befriending Number 5. It remains unclear however if this movie will be a sequel to the first two movies, or a remake of this movie.
In this film and Short Circuit 2 (1988), Johnny 5's voice is provided by puppeteer Tim Blaney. This casting decision was made due to the director's belief that real-time interaction with the robot prop would make the interaction seem more natural on-screen than if they edited Johnny's voice in during post-production.
Fisher Stevens plays a character called Ben Jabituya, who has an exaggerated Indian accent and mannerisms. However he is not Indian. When asked where he is from, he responds Bakersfield, and that his ancestors are from Pittsburgh.
The Soviet T-72 tank destroyed by the robots during the testing ground demonstration at the beginning of the movie is actually a fiberglass mock up built on the chassis of a U.S. M-41 Walker Bulldog tank. As the movie was made during the cold war years actual Soviet equipment was not obtainable in the west.