When Pikachu is given a Thunder Stone, Pikachu evolves. Pichu is Pikachu's pre-evolution, and is evolved into Pikachu when it has high friendship and levels up. It evolves into Pikachu, and can evolve into Raichu by using a Thunder Stone. Pikachu can evolve into Raichu without having to meet any condition for evolution. The evolution can then be carried out at any time, but some players like to teach certain moves to Pikachu before evolving it. If there is a regional form available, Pikachu can evolve into a different region's form in the Pokémon games, depending on the game and the regional form.