Christopher Reeve bowed out just before filming began. Superman's absence is explained early on by a radio broadcast that says he is in a far off galaxy, on a peace-seeking mission.
Helen Slater had to train three hours a day for three months to do the outdoor flying sequences, where she was suspended by wires from a 200-foot tower crane.
According to behind-the-scenes footage included on the DVD release, a very different Supergirl costume was planned. It was based on the revised Supergirl costume in the DC comic books beginning in the early 1980s. Differences included a headband and curly hair.
There were approximately five script re-writes before filming began. In one version of the script, the film was going to begin with the destruction of Krypton from Superman.
The movie was completed by Warner Brothers. After Superman III, Warner Brothers decided not to release it. Tri-Star Pictures picked it up, and cut it from 126 minutes to 105 minutes.
The dean of the college that Linda Lee attends is named Mr. Danvers. In the Supergirl comics, Linda was adopted by a family named Danvers, and even adopted their surname, Linda Lee-Danvers.
Brooke Shields was the first choice for the role of Supergirl, and Christopher Reeve was going to have a substantial role. The original script had Supergirl trying to rescue Superman who had fallen ill due to Selena's magic.
With a total domestic gross of $14 million, this movie made the least money of all the films in the Superman series, just behind Superman IV: The Quest for Peace which made $15 million. The budget for Supergirl was $35 million.
Helen Slater's film debut. Many years later, Slater made a cameo appearance in an episode of Smallville, playing Lara, the Kryptonian mother of Kal-El/Clark Kent, in a flashback scene.
Dolly Parton was offered $7 million to take the role of Selena, but she turned it down, claiming that she couldn't play a witch, no matter how much money was offered. Jane Fonda and Goldie Hawn also turned the role down.
Ilya Salkind's partner, Alyssa Cartagena, was the original producer. During pre-production and principal photography, there was much tension between Cartegena and Alexander Salkind. Cartegena was not pleased with the script or the film's publicity campaign. Eventually she was replaced by Timothy Burrill, the co-producer. Cartegena was very resentful; she had secured most of the film's financing and was responsible for bringing Faye Dunaway on board.
When Linda Lee and Lucy Lane first meet, Lucy is reading a comic book starring The Incredible Hulk, published by DC's rival, Marvel. Also ironic because The Incredible Hulk faced off against Superman in the 1996 Marvel vs. DC crossover.