As per the 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 Director John Badham and the Robots Designer Syd Mead, 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 and camera coverings.
In this film and Short Circuit 2 (1988), Johnny 5's voice was 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.
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 to be remarkably effective in getting just the right look needed for the scenes.
Major confusion occurred in India among fans when this movie was released. Many people who had seen the film thought that Fisher Stevens (who played the part of an Indian) was actually Bollywood actor Javed Jaffrey. This was due to Javed being the spitting image of Fisher Stevens, with his beard and round eye glasses. Javed had just had his first release, Meri Jung (1985). In the film, he sported round eye glasses and a beard. When this movie released in India, many thought Javed had acted in a Hollywood movie. It was only after Javed confirmed in interviews that another actor starred in this movie, that people finally knew the truth.
Any time you see Number 5's arm or hand doing something without the rest of him in the frame, its because the robot puppet was not capable of doing the action. Like rolling up the window, opening storage compartments, et cetera.
There was a script for a possible third Short Circuit movie written in 1989 and re-written 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.
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.
In a scene that was cut from the film, Number 5 encounters a Omnibot that attempts to give him a beverage. An Omnibot was a toy robot manufactured by Tomy in the mid 1980s. The deleted scene was seen during the end credits.
The Soviet T-72 tank destroyed by the robots during the testing ground demonstration at the beginning of the movie was 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, real Soviet equipment was not obtainable.
One of the subtle ways in which the movie shows Number 5 becoming alive is his gradual transition from referring to himself in the third person to the first person, implying a development of self-awareness. This is particularly evident when he says "I am alive" to Crosby after repeatedly saying "Number five is alive" earlier in the movie.
At the point where Number 5 first hears the El DeBarge song "Who's Johnny" while driving the Nova van, the original choice of song for that section was the Dire Straits song "Money For Nothing", but unfortunately getting the rights to use that song was deemed to be too costly.
When the dance sequence was filmed, John Badham danced with Ally Sheedy as they talked through and rehearsed the scene which Johnny 5 dances with Stephanie to "More Than a Woman" by The Bee Gees. The song was featured in Saturday Night Fever (1977), which was also directed by Badham.
Puppeteer Tim Blaney was selected to voice and operate Number 5 on set, after John Badham heard Blaney's robot voice and liked it. Blaney was originally intended to supply only a placeholder voice for Number 5 during filming, which was to be dubbed over later by another voice actor. After three months of filming, the crew got so used to hearing Blaney's voice as Number 5 that they could not imagine anyone else in the role, and so Blaney was officially cast.
In 2015, comedian Aziz Ansari had a discussion with Fisher Stevens about Stevens (who is Caucasian) playing the role of Indian American scientist Ben. Ansari said that he grew up strongly disliking both the role as a stereotype and Stevens for ever accepting it, but he felt Stevens was not a villain after talking to him, and simply an actor who needed a job at a time when cultural considerations were simply ignored in making movies. Stevens described how he did research to make Ben into a non-stereotype and that he regretted how the character made people of South Asian descent feel. In the end, Ansari and Stevens agreed that if SHORT CIRCUIT was either a new film or a remake in the present day, the role of Ben should and would be played by an actor with a South Asian background.