Wild Pokémon
Wild Pokémon (Japanese: 野性ポケモン Yasei Pokémon) are any Pokémon that have not been caught by a Pokémon trainer. They are encountered by walking in tall grass or caves, traveling with Surf, headbutting trees (in Generation II only), breaking open rocks with Rock Smash (in Generations II and III), or by fishing. Wild Pokémon can also appear when using Sweet Scent, whilst standing stationary in grass.
Wild Pokémon can be caught using a Poké Ball.
Generation IV
In Pokémon Diamond and Pearl, wild double battles were introduced. There are five instances that this can happen.
The protagonist will encounter another character that needs help getting through the said location. When the trainer encounters a Pokémon with this person, it will be a wild double battle.
When this wild double battle occurs, the protagonist cannot capture a Pokémon until one of them has fainted.
