if you have a celebi on heart gold or soul siler, take it into ilex forest and talk to it. then see what it does.
if you already know about this then rar, i found out by just taking my celebi into ilex forest for lulz since it's the protector of the forest.
either way.
it was awesome for me since i just got origin forme giratina non hack on soulsilver at the ruins of alph/sinjoh ruins. i thought it would be like level 70....it was level 1 since arceus is a butt hole and makes pokemon eggs and ruins your life. the twat