Early designs of the characters more resembling the 40s cartoons.
- Adam Baldwin was the first choice for the role of Clark Kent before Tim Daly was cast. Baldwin would eventually go on to voice the titular character in Superman: Doomsday.
- Sherman Howard read for the role of Lex Luthor before the casting of Clancy Brown. Howard previously portrayed the character in The Adventures of Superboy, and would later go on to voice Derek Powers in Batman Beyond.
- James Belushi was originally cast as Parasite, which got as far enough as press material and early commercials. For unknown reasons, he was replaced by Brion James at the last minute.
- An early idea was to have the series be a Team-Up Series, with each episode featuring Superman partnering with different members of the Justice League. Timm did up Concept Art of a number of different heroes like Vixen, Mister Miracle, Orion and Lightray of the New Gods, The Question, Nightshade (who would've sported a Psylocke-inspired outfit), and Black Lightning. The idea was jettisoned out of fear that Superman would be overshadowed in his own show.
- The intro was originally supposed to be a montage of Superman performing heroic deeds. However, for whatever reason, this was mostly scrapped in favor of using series clips; the only original footage in the intro wound up being the bit where Superman flies across the city at night, and the very end as the camera zooms in in the S-crest.
- "The Prometheon" was originally supposed to end with other aliens finding the dormant creature and accidentally awakening it again, but it was cut because the episode was too long already.
- Paul Dini and Bruce Timm originally wanted to use Kara Zor-El as Supergirl, but they were denied by DC Comics due to the then-current "Superman is the only survivor of Krypton" edict. Although they went as close as they could get, with Kara being Clark's adopted cousin and from Krypton's "sister planet", Argo (a Mythology Gag to that side of the House of El living in Argo City in the comics), essentially making her as close to Kryptonian as possible. An additional Mythology Gag is her family name - Kara Zor-El's mother was named Allura In-Ze, with said surname given to the show's interpretation of Kara.
- Cat Grant was originally meant to be part of the main cast and even had a character design done up for her but she was dropped in favor of Angela Chen. Grant's design reportedly can still be seen in the series in various scenes. Had she been retained for the cast Cat would have served as a rival to Lois for Clark/Superman.
- The original plan for "Apokolips... Now" had Ma and Pa Kent killed instead of Dan Turpin, but DC said they would need to bring the Kents back to life if that happened. Since Bruce Timm wanted to avert Death Is Cheap the target character was switched.
- Prof. Hamilton was also considered to be killed, but the staff didn't particularly like him as a character and didn't know if they could make his death tragic enough as a result.
- The original, much darker plans for "Little Girl Lost" involved Superman discovering that Darkseid was turning humans into Parademons, with heavy Nazi overtones for the transformation camps, and the episode ended in the midst of a large scale battle on Apokolips. The authors do like the finished episode, but were very disappointed with the heavy backtracking after they had already been given the go-ahead for the initial plot.
- "Legacy" was intended to kick off a season's worth of episodes about Superman regaining the world's trust. However, a pushback and other projects (Batman Beyond) led to it being produced as the finale instead while the theme of public distrust for metahumans became an underlying plot thread in Justice League.
- Lex's robotic Tyrannosaurus rex was going to be given by Superman to Batman - a modern twist on one of the Batcave's most iconic trophies. Ultimately, though, the DCAU never really depicted the Batcave's trophy room outside of a few cameos in Justice League and the tie-in comics◊.
- The original ending to "A Little Piece of Home" would have also included Superman giving the piece of Kryptonite from the episode to Batman for safe keeping.
- There were some art sketches of girls for the strip bar scene in "World's Finest". They wore nothing but black bikinis and long black leather boots. The final cut of the episode had the girls in flirty dresses instead.
- During the development phase, they considered making the show a period piece and even initially designed the characters with a look that would have fit more in the 1940s.◊ note The idea was scrapped because they didn't want the show to be compared to the Superman Theatrical Cartoons and went for a more modern look instead.
- An interview with Dan Riba revealed how General Zod and Ursa would've appeared in the series, even going as far as to have character designs. They were then scrapped. Dan thought that they were rights issues involved with Zod.
- Bruce Timm wanted Perry White to be black, but was vetoed. Funny how that worked out.
