Set to launch on December 7 for Nintendo Switch, Super Smash Bros. Ultimate will include every single fighter ever featured in the series’ nearly two-decade run, making it one of the biggest crossover events in gaming history. Fans can enjoy returning favorites like Pikachu, Pikachu Libre, Jigglypuff, Pichu, Lucario, Greninja and Pokémon Trainer, who fights by making commands to Squirtle, Ivysaur and Charizard. According to the official Super Smash Bros. blog, Greninja turns into Ash-Greninja during its Final Smash. There are also numerous Poké Ball items that players can use to their advantage, including Mimikyu and Ditto:
Ditto will transform into the fighter who threw the Poké Ball when joining the fight. After the transformation, Ditto will have the exact same abilities as the original fighter!
Source: Official Super Smash Bros. Blog