Arnold Schwarzenegger's character was originally intended to be a reprisal of Conan, star of the comic book in which Red Sonja first appeared, but the film did not have the rights to this name. An unofficial explanation endorsed by fans is that Kalidor is one of Conan's "traveling names," a common feature of multi-national mythical/legendary heroes such as Zeus aka Jupiter and J.R.R. Tolkien's Gandalf aka Mithrandir.
Arnold Schwarzenegger himself eschews this movie as one of his worst, yet he (laughingly) claims that it's an excellent disciplinary tool for his children: "I tell them, if they get on my bad side, they'll be forced to watch Red Sonja (1985) ten times in a row. Consequently, none of my kids has ever given me much trouble."
Arnold Schwarzenegger signed up for a glorified cameo, as a favor to producer Dino De Laurentiis. Much to his surprise, he was stuck on the set for four weeks, three weeks longer than expected. He discovered after watching a rough cut of the movie that his role had been expanded to co-star, thanks to crafty angles and multiple cameras. Soon after, Schwarzenegger decided to terminate his 10-year contract with De Laurentiss.
In 2009, a remake of the film was announced, with Robert Rodriguez to direct and Rose McGowan to star as Red Sonja, succeeding Brigitte Nielsen in the role. However, due to the failure of the 2011 remake of Conan the Barbarian (2011), production was abandoned and both Rodriguez and McGowan backed out of the project. As of 2015, the remake is in development hell.
It is commonly believed that Robert E. Howard created the character of Red Sonja in one of his Conan short stories. In reality, he created a character with a similar name (Red Sonya) appeared in "Shadow of the Vulture," a story set in 16th-century Turkey with no Conan connections. This was the namesake of the famous "Red Sonja" who first appeared in a Conan comic book written by Roy Thomas and illustrated by Barry Windsor-Smith.
The western Hannie Caulder (1971) is considered a possible influence behind the film. In that film, Hannie Caulder, the red haired main protagonist (Raquel Welch) learns to use a gun and becomes a vengeful gunwoman, as she sets out to seek revenge upon the three outlaws who raped her and killed her husband and is joined on her quest for revenge by a bounty hunter (Robert Culp).
The original theatrical trailer of this movie contains cutting room-floor footage of scenes glimpsed only briefly in the film's prologue: Sonja, left to perish in her burning home, is saved by her dying brother Barlok; Gedren, prior to her disfigurement, addresses her soldiers and slaves.
The name of Ronald Lacey's character, "Ikol," spelled backwards is "Loki." Loki, in Nordic mythology, was the God of Evil and Corruption, infamous for being a jealousy-prone troublemaker, and plays a pivotal role in the End of the World.