Tim Daly said the reason he signed on to do Superman's voice in this series was because he thought it would be fun to play a superhero in a superhero cartoon. He later said he underestimated just how difficult voice acting for a superhero, especially one of Superman's stature, would be.
Like the Joker's henchwoman Harley Quinn, Lex Luthor's henchwoman, Mercy Graves, is a character originally created for the show. Like Quinn, she was eventually added as a member of the cast in the comics. The comics version of Mercy has blonde hair and does not wear a chauffeur's uniform.
The opening sequence never displays the title of the show and is the first opening sequence of any Superman cartoon to not verbally explain where Superman came from, his extraordinary super powers and his secret identity. The producers of the show thought Superman is a well-known icon and the opening sequence of the show visually displays everything you need to know about the character without having to verbally explain it to the audience.
Originally, producer Bruce Timm was going to style this series after Max Fleischer's Superman cartoons, which he previously used as the visual basis for Batman: A Série Animada (1992), but he decided to use a futuristic look to the series that the producers called "Ocean Liner Deco." The reason why they didn't make it Fleischer-esque is that Timm didn't want anybody to literally put it side-by-side with the old Fleischer shorts and say, "They're just doing a third-rate knockoff of the Fleischers." Alex Toth thought the series should look like the Fleisher version and disagreed with this decision on the art. Because of this, Toth never spoke to Timm again.