When asked if Nathan Fillion's Guy Gardner would have his iconic bowl cut in the film, James Gunn replied "Giving my old pal Nate a bowl cut might have been my primary reason for casting him."
James Gunn has assured fans that the movie is not a comedy and that, despite adding several other DC Comics characters, the story focuses on Clark Kent/Superman and Lois Lane.
James Gunn tweeted that the death of his father was an influence on the screenplay. The film's release date, July 11, 2025, was his father's birthday.
The inclusion of Nathan Fillion as Guy Gardner marks the seventh time that Fillion has appeared in a film directed by James Gunn, continuing the tradition of the actor making an appearance in every one of Gunn's films, owing to the pair's longtime friendship.
The first Superman film to be written by one person, as well as the first one to be written and directed by the same person. Superman and the Mole-Men (1951), the first Superman film, was written by Robert Maxwell and Whitney Ellsworth under the pseudonym "Richard Fielding."