I know this is the third time but i think that the GS ball will be over wi-fi or..
when you beat the elite four professor oak will say he has obtained a pokeball which he wants you to take to kurt then you can catch celebi
yes it is a game that when you play it on a dsi it has extra features which cant usually be unlocked
source- Ive got a dsi
:grog::bidoof: my two favorite things smileys, and BIDOOFS!!