event or gameshark gameshark: walk on water to an island in the north and catch him
needan action replay only other way
you can't catch it until you don't have a gameshark because its impossible to catch without gameshark
SHORT ANSWER: You can't. LONG ANSWER: You can use a gameshark or AceKardi, but i assume that by action replay you mean a chearting device.
Nope not without a gameshark
get a darkrai from your friend[note if they want to trade)
you can not catch Darkrai in platinum you can only get it at special events or you can go to GTS and trade someone for it the last option is to get from a friend or use a master ball on a wild Darkrai or on someones caught Darkrai.
you don't. It catches you
You can't catch mew without a ticket. You can get it from gameshark or trade it from another game, but you can't catch it.
No not without gameshark, Action Replay or Trade
not without a gameshark
All if you have a gameshark