While looking through the files on the Star Wars Episode 1 racer disk for Dreamcast (using the serial cable) I noticed two files named SW_DISCO.AFS and SW_PARODY.AFS
Heres the cool bit, the first one is a Disco remix of the starwars theme tune (very cool) and the other is a parody of Copacabana by Barry Manilow called "Star Wars Cantina". These songs are not accessible via the game as far as I know and are normally inaccessible to PCs too, so in effect they were hidden very well. And to top it all off, they were not standard files, but encrypted AFS files (sega's special sounds format).
I also found a picture of Bill Gates on the game "Toy Commander", hidden very deep down and disquised as a .txt file. Very strange.
Anyone else have any amazing tales like this?
P.S. I can post those MP3s if there is enough interest