Mega Evolution

Mega Evolution is a gameplay mechanic in the Pokémon series, introduced in the sixth generation of games, which transforms a select Pokémon into a more powerful form. Mega Evolution requires the Pokémon to be holding its corresponding Mega Stone, and for the trainer to have a Key Stone.

In Super Smash Bros. for Nintendo 3DS / Wii U, Lucario and Charizard use their Mega Evolutions as their Final Smash attacks, transforming into Mega Charizard X and Mega Lucario, respectively.

Mewtwo also Mega Evolves during its Final Smash, but unlike with Lucario and Charizard, Mewtwo's Psystrike is an offensive attack, instead of an actual transformation.