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.
This series was made to coincide with a new Superman film titled "Superman Lives" (originally titled "Superman Reborn"). However, the film would spend years in development hell and would be eventually released years later as Superman Returns (2006).
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.