In the Dream World you will sometimes find Pokémon. These Pokémon usually are not available within the region of Isshu, which therefore are Pokémon from the regions of Kanto, Johto, Hoenn and Sinnoh. Once you have befriended these Pokémon you will then be able to enounter them in a certain part of the Isshu region and will be able to capture them.

Some of the Pokémon that can be caught in the Dream World have abilities that are not in the previous games. As such this is one of the ways to be able to obtain the Pokémon with a special ability.