There are 3 hidden chao eggs. 1 hidden in every adventure field. Here's how to find them.

Station Square: Near City Hall, in the grassy area, there is a rock. Pick it up. Now go to the store with the golden treasure thingy on a stand. That is the egg. Unfortunatley, you can't just grab it and leave. When you get there, remove the golden egg from the stand. Now put the rock on the stand. Now you can leave. Leave, go to the garden, and hatch the egg.


Mystic Ruins: This is easy. Go to the waterfall and stand in front of it. Do not move. Eventually, in about 5 or 10 seconds, a silver chao egg will fall from it. You can't pick it up yet. Wait until it stops floating. Now you can pick it up. take it to the garden to hatch it.


Egg Carrier: This is even easier. You need to be Amy. When you're in the prison room, the jail cell next to the one you were in at the beginning of the game has the egg. There is a button switch in front of it. Jump on it. The jail cell opens up. Take the egg, and go to the garden to hatch it.