See below as this question has been asnwered. You need to take good care of your chao in both its first and second life. In the second one it will morph into a different one depending on its side.
I've went to all different sites of how to get the chaos chao. Some said to reincarnate a chao twice, feed it all 21 animals and feed it a dark,hero,or chao fruit and others say not to feed it those but pet it 25 times depending on which side your on. I don't know which one is the right way.