Pokémon World was an area that was originally accessible from the Highway, but has since been removed in newer versions of Yume 2kki. The area was given this name because of its use of sprites from the Pokémon Game Boy Advance games.
Desu-chan and Onee-chan were found here, in first releases close to the area's entrance, and in later ones down an infinitely looping path that could only be bypassed with the penguin effect. Onee-chan sat on a bench holding drinks while Desu-chan would wander around. They are presently found in a rest area on the south east road of the highway.
The Fairy effect was also originally found here, in a chaser guarded maze where you would have to catch it , but was imprisoned in a cage in the Black Building in newer versions.