The Bonus Disc could be obtained only in Japan and the United States having booked the Pokemon Colosseum.
The CD contains a demo of Pokemon Colosseum and the movie, Pokemon Jirachi Wishmaker. Also u could get special Pokemon, depending on the version:
In North America, u get Jirachi being one of the few ways to get it legally.
In the Japanese version, u can get to Celebi and u can buy when u have purified the 48 Shadow Pokemon. u can also get a Pikachu with Light Ball.
Keep in mind that these Pokemon can be transferred only to versions of Pokemon Ruby and Pokemon Sapphire that are in the same region, having the same language, otherwise the transfer will not be achieved.
Bonus Disc Of The Movie, Pokemon: Jirachi Wishmaker