During the transistion between each version, Mushroom Kingdom Showdown has had content replaced or dropped entierly from the game.
Back when Mushroom Kingdom Showdown was called MARIO Smash Bros, Mario had a whole new sprite set based on his appearance in Super Smash Bros. Brawl. In the later versions, it was changed to a more cartoony version to match with the other characters.
Mario originally had a green and yellow skinswap based off of Luigi and Wario. It was removed in later versions to be replaced with a improved Wario costume and a Fire and Ice Mario costume.
In v.0.9, Donkey Kong got a massive change with a new, smaller design, this done so his sprites would fit the other characters' style.
Master Hand was the final boss for Classic Mode in v.0.4. He is from the Smash Bros series, where he appears (sometimes along with Crazy Hand) as the final boss in Cassic Mode. Master Hand was replaced by a random character fight in v.0.5, and then finally Giga Bowser in v.0.6.
Unused CharactersEditFour unused character icons have been found in the game's files, these include Nabbit, Classic Mario (or C. Mario), Goomba and Sakurai (joked on an update video). A sprite for Nabbit can also be found in most stages, along with a walk cycle.
Mushroom Plains and Boss Stage have the most redesgins. At first, Mushroom Plains was a very plain hand-drawn stage and later got updated in v.0.6, with a more New Super Mario Bros. feel. In v.0.9., it was redesigned again to have Peach's Castle in the background and pipes for walls instead of bricks. The floor was also changed to a more detailed version of what it was in New Super Mario Bros.
The Boss Stage followed the redesgins with the old hand-drawn and the New Super Mario Bros. design each with a purple tint.
In v.0.9, Platform Castle got a small yet indepth redesign with more texture in the floor.
Unused Stages Edit
Within the files of the game, two unused stages were discovered: TEST STAGE, a battlefield stage from Super Smash Bros: Cruel; and Yoshi's Island, from Super Smash Bros. Brawl.1-Up Mushroom in later versions.