Concept Art for the character Honey Bunny who was later replaced by Lola Bunny.
- Joe Alaskey said in an interview he initially expressed interest in voicing some of the Looney Tunes for this film (or at the very least, provide Daffy's voice). But, despite the fact that Alaskey had several years of experience doing spot-on renditions of Mel Blanc's characters, producer Ivan Reitman kept making him audition several times, and flip-flopping back and forth as to whether or not he should be cast. Alaskey finally got fed up and said, "Look, either you want me, or you don't!" Alaskey didn't hear from Reitman again after that. In the end though, Alaskey admitted he was glad he wasn't involved in Space Jam after seeing the movie and not liking it.
- Noel Blanc (Mel Blanc's son) was also supposed to provide the voice of all of the regular Warner Brothers male cartoon characters, but he and Warner Brothers couldn't agree on a contract, so the studio replaced him with Billy West (Bugs Bunny and Elmer Fudd), Dee Bradley Baker (Daffy Duck, The Tasmanian Devil and Toro), Bob Bergen (Marvin the Martian, Porky Pig, Tweety Bird, Barnyard Dawg, Hubie and Bertie), Bill Farmer (Foghorn Leghorn, Yosemite Sam and Sylvester) and Maurice LaMarche (Pepé Le Pew).
- Originally, Honey Bunny from the Looney Tunes comics was going to be Bugs Bunny's female counterpart, but she never went past the designing phase because she looked too much like him, so Lola Bunny was created to fill in the female gap. Though early on, Lola did have grey fur like Bugs and red hair
before being changed to peach. She also had a full head of long hair at one point. And as shown in an even earlier concept design, Lola was going to be a redesign of Daisy Lou from "Hare Splitter", but then was going to be Lola Rabbit. - This early test animation shows that the main villain Swackhammer had a different design and was originally voiced by Jack Palance.
- Swackhammer was originally going to be depicted as live-action but the idea was scrapped.
- Luis Alfonso Mendoza, who was the Latin American Spanish voice of Bugs Bunny from 1997 until his tragic murder in 2020, was selected to voice the character in Space Jam but he was unable to reach an agreement to the dubbing studio at the time, Audiomaster 3000. Consequently, Alfonso Obregón Inclán would provide Bugs's voice in the film.
- Joe Pytka wanted Michael J. Fox to play Stan, but he was overruled by the studios. Chevy Chase and Jason Alexander were also considered.
- There was originally going to be a scene in the movie featuring MC Skat Kat and the Stray Mob, an animated hip-hop group who worked with Paula Abdul on some of her music videos, but it was completely cut out of the script.
- If Bill Murray had turned down his role, Road Runner would have appeared in his place.
- Joe Pytka revealed during an interview with ''Entertainment Weekly'' in March 2021 that the film was originally supposed to end with Michael Jordan's baseball match in which he succeeds in hitting a home run and also having a Shout-Out to The Natural, instead of a Time Skip where he ends his retirement from basketball and plays with the Chicago Bulls. The baseball ending was filmed, but left on the cutting room floor much to Pytka's disappointment.
- D'Angelo had originally recorded "Playa Playa" for the soundtrack, but the suits at Warner freaked out when they heard it, according to co-writer Questlove. As a result, D'Angelo instead gave them "I Found My Smile Again", a re-working of an unreleased track from his debut LP Brown Sugar. "Playa Playa" would later be released on his sophomore album Voodoo.
- According to the Space Jam website, the Monstars all had different names in development. All five were named after different words for "nothing": Bupkis, Nada, Null, Void, and Zilch. Out of all of these, only Bupkus kept his name. This does explain why they all have the number 0 on their uniforms.
