They stopped doing transformations
One source states, "The latest Smash Bros. games for the Nintendo 3DS/Wii U are some of the most technically impressive in the series to date. The games have the biggest roster of characters in the entire series. The Wii U version has incredible HD graphics, while the 3DS version allows you to play the game online whilst travelling.
Despite the technical advancements that the series has achieved, the latest Smash Bros. games had to drop a major feature in order to be playable on newer systems - the transforming characters.
In the previous Smash Bros. games, some of the characters could change into entirely new ones. Princess Zelda could transform into Sheik at any time (and vice versa). The Pokémon Trainer could switch between three characters at any time. Samus would become Zero Suit Samus after using her Final Smash (and vice versa).
Sakurai wanted to make sure that the 3DS version of the game would run smoothly with the full 3D effect activated. One of the biggest drains on the hardware was having to load an entirely new character. It is for this reason that the Pokémon Trainer was scrapped (with only Charizard remaining). Princess Zelda & Sheik and Samus & Zero Suit Samus were made into separate characters"(Baird).
