Monster Rancher, known as Monster Farm in Japan, is a multimedia series developed and published by Tecmo. The series began with the release of Monster Rancher for PlayStation on July 24, 1997. Players could acquire monsters by using real CDs. When a CD was inserted into the console, the game would use its metadata to create a new monster. The type of CD mostly didn't matter but there were a few fun Easter eggs such as Christmas albums would result in a "Santa" type monster and inserting the Tecmo's Deception: Invitation to Darkness game would result in Ardebaran becoming a playable monster.
I remember when my friend got this. The only really interesting thing it had going was the novelty of scanning CDs to unlock characters. I don't remember the gameplay at all beyond that. I recall thinking the art and characters were pretty ugly though..
I will say, I did like the animated show.