Super effective indeed.
Pokémon Trainer's Final Smash. Squirtle, Ivysaur, and Charizard all come out of their Pokéballs and attack in a combined beam of Hydro Pump, Solar Beam, and Fire Blast. In typical Pokemon fashion, a speech box appears, announcing the 3 Pokémon's Final Smash.
If used on flat stages such as Pictochat, Final Destination, or Bridge of Eldin, it is virtually impossibble for an opponent to dodge this Final Smash. (Unless Opponet is up in the air while the attack is on the ground.)
You can obtain a trophy of this Final Smash by completing All-Star Mode with Pokémon Trainer.