I'm tearing my hair out over this, so I'm going to pose this to you guys.
I remember going to a friend's house and him playing a game that was like Pokemon, but not actually Pokemon franchise. It seemed to be more...plant based. I believe the word "kakuna" or something similar sounding were in the title. Anyways, all I can remember is that you could breed one monster with another. Each monster had a little four-pointed diagram that displayed their inherant "elemental" property. The shape would warp more towards a certain side of the diamond to show how much that monster was affiliated with that element.
It came out around about the time Pokemon first started becoming popular in England (about 2000ish). I'm 86% sure it was a PSX game, though my friend also owned a Dreamcast, so it very well could be a Dreamcast game as well.
Anyone got any ideas as to what the hell I'm talking about?