Monster Rancher (Monster Farm in Japan), is a "monster raising" simulation in which you raise your monsters in order to win fighting tournaments and become the greatest breeder ever.
A unique feature is the way you obtain your monsters: from every CD you own. That's right: every CD you own (including PC ones, musical and even 3D0 games) can be used to generate a different monster.
Source: The Game Website.
Interesting support site at
Monster Rancher Metropolis