Here's a little something to bring Sonic's Nintendo opposite into the game and give him some (perhaps undue) spotlight! This mod swaps out Sonic, Tails, and Knuckles with Mario, Luigi, and Wario respectively to allow you to do a full crossover of the Mushroom Kingdom into the Sonic's speedy world. Be aware, this mod requires the Sonic Mania Mod Loader in order to work.
Credits: MetalKingBoo