Check out the Lost Media Wiki’s article on the 101 Dalmatians: The Series’ unaired pilot!!!
Much like how Disney's Recess originally began production with a pitch pilot that would remain untelevsied indefinitely, 101 Dalmatians: The Series was first pitched as a pilot or "demo" to Disney in assumedly 1996, seeing how the live-action film it was partially based on came out in that year. The Recess pilot was pitched at that time and both the pilot had to be finished and the show had to be started by early 1997.
Unlike the Recess pilot however, this wouldn't be later adapted into an episode of the TV show. The characters and animation isn't too dissimilar to what would be in the final product and not too much is known about it, other than the fact it was possibly going to have another main character called Penny, as that was what the show was originally going for until she was scrapped. This is evidenced by an artist drawing the removed character in a sneak peek for the series (twinned with Recess) in-between clips of the pitched pilot which was released on 1997 VHS releases of 101 Dalmatians (1996) and Doug's Birthday Blues as a promo for ABC Saturday Mornings. And unfortunately, those clips are all that is known about this pilot.