In Poképark 2 you don't only play as Pikachu, you can also play as the three starters from Black & White. Each one of the four Pokémon have their own moves to use in battle. They also have an enhanced move to do tasks which none of the other playable Pokémon can do. Therefore you have to switch Pokémon during gameplay to progress at certain points.
It is not known yet to have a special ability, but Pikachu can carry Pokémon and various items.
Tepig have the ability to crush certain big rocks placed around the island with the ability Flame Charge.
Snivy can increase the height of his jumps with the help of the move Leaf Tornado, making it possible to reach higher points.
As Oshawott is a water Pokémon, he's the only one of the four that can swim in water and meet Pokémon.