Retro user Orengefox posted on the forums his discovery of two Japanese prototypes of Sonic Adventure and Sonic Adventure 2 on Sega Dreamcast. Both of which have a potential source of content that are missing from the final builds with the Sonic Adventure Auto Demo showing some good promise. The Sonic Adventure demo dates back to October of 1998 shown to press and ran automated showcase of cutscenes, the different characters and gameplay footage running in real time. Back in 1998, this was something to behold for the press eager to turn around any and all information of Sonic’s first true 3D Adventure.
The Sonic Adventure 2 demo dates back to May of 2001, 26 days before it’s release in Japan, and worldwide, which features three levels playable. One for Sonic, one for Shadow and one to showcase the two player mode. Similar to the disc sent out to English-speaking press, this one for the Japanese press.
Already Retro members have gone and dug around and found some notable differences such as this work-in-progress version of the Chao Garden theme (Credit to Retro user evilhamwizard) for the first Adventure title. You will find plenty more in both respective topics such as video footage, unused graphics and more.