The movie's original budget was $36 million. Just before filming was to begin, The Cannon Group, Inc., which was experiencing financial problems, slashed the budget to $17 million. The filmmakers cut corners by doing things like re-using special effects.
Richard Donner, who'd been fired from Superman II (1980), was offered the director's chair; he declined. Donner, at the time who was originally directing the first two Superman movies, was planning to make and produce at least four Superman films.
Christopher Reeve's flying harness was concealed under a larger version of the red shorts he wore for the costume, making his waist look bigger. In previous Superman movies, the bigger waist was hidden by the cape, quick cuts, or creative camera angles. In this movie, the bigger waist is clearly visible, leading some reviewers to speculate that the thicker waist was Reeve's actual waistline.
Originally, the film had two Nuclear Men. The first, dubbed Nuclear Man 1, wore a black costume. His scenes were filmed, but eventually cut, allegedly because previews revealed several serious visual effects errors. The deleted footage was considered for a fifth Superman film.
The Cannon Group, Inc., thinking that they had a potential blockbuster on their hands, cut the two-hour-plus film down to a lean ninety minutes, so that theater owners could have more screenings per day, and potentially make more money that would eventually filter back to the studio.
In the original script, Superman was supposed to rebuild the Great Wall of China at super speed, but when money problems emerged, they had Superman use his "magical rebuilding power" (which had been completely made up for the film). It required only that Director Sidney J. Furie run the camera in reverse, rather than a complicated super-speed scene.
Before this film was released, The Cannon Group, Inc. began planning a fifth film, directed by Albert Pyun. When Cannon went bankrupt, Superman's film rights reverted to Ilya Salkind and Alexander Salkind. Ilya wrote a story for a fifth film with Cary Bates and Mark Jones, in which Superman dies and is resurrected in the bottled city Kandor. It was not an adaptation of the famous "Death and Return of Superman" story arc, which it predated by about two years.
Christopher Reeve approached Tom Mankiewicz, creative consultant for the first two Superman films, to pen the screenplay for this film. He declined, but suggested for this film that Superman deal with a human conflict that even his superpowers can't control. It formed the basis of Superman challenging the nuclear arms race.
Much of the special effects crew that worked on the first three films and Supergirl (1984) were hired during pre-production, but eventually left following salary disputes. Only Roy Field would remain loyal to the production.
At the end of the film, Superman says to Lex Luthor as he's dropping him back off in the prison quarry, "See you in twenty". Superman and Lex wouldn't appear in a feature film together until Superman Returns (2006).
Supergirl (1984) is not mentioned anywhere during the film. The spin-off film was released between Superman III (1983) and this film. Christopher Reeve was originally going to make a cameo in the film, but passed.
The shots of Superman using his "wall rebuilding vision" to repair the Great Wall of China, are just re-purposed footage of him waving at the people, in fact it's the same shot used twice, with it being mirrored the second time to hide the fact that it's repeated (this is apparent from the parting in Superman's hair switching sides between shots). He was originally scripted to fix it at super speed but the VFX budget couldn't accommodate that effect.
When Superman makes his speech at the end of the film, he paraphrases Dwight D. Eisenhower when he says, "there will be peace when the people of the world want it so much that their leaders will have no choice but to give it to them."
No soundtrack release to this film was released for over twenty years until Film Score Monthly issued an 8-CD box set called "Superman: The Music (1978-1988)", which presents the complete score to this movie.
When Jeremy appears at the press conference, his response to the reporters is "I wish Superman would've said yes." The Daily Planet publishes the headline as "Superman Says Drop Dead to Kid!" In 1975, when New York City was facing bankruptcy, Mayor Abraham Beame asked the government for a federal bailout, and President Gerald Ford gave a speech denying federal assistance to New York City, and the New York Daily News published the story with the headline "Ford to City: Drop Dead", misquoted words which Ford never himself said when turning down New York City's request for federal relief.
The final Superman film, in the Salkind period version, and the only one not to be shot at Pinewood Studios, from this period. The infamous Superman IV would be shot at the Cannon Elstree Film Studios, as by 1987 the Salkinds sold the Rights onto Cannon Films, who had themselves by then had acquired the old EMI Elstree Studios, previously known the Star Wars and Indiana Jones film base, which in turn would ultimately lead to half of Elstree Studios being demolished for the Tesco Supermarket in Borehamwood.
Sidney Furie directed this movie. This is the same director that Warner Brothers had lined up to direct The Godfather, before they decided to go with Coppola at the last minute; not because he had such an impressive film pedigree at that point (his major film credit at that point was Finian's Rainbow); but because he was Italian; and they thought that would give the proceedings an authenticity and gravitas that were not there if he were not Italian; it would also lessen the perception that Warner Brothers was slamming Italians with this movie if it had an Italian director. Who knows how Godfather would have turned out if Furie had directed it; as originally planned.