But how do you get a darkrai in the first place??
Can you clone without wi-fi?
Darkrai could have been obtained through the Japanese event, which would have been Movie Event 7 I believe though getting one of those is very rare. Or you could have obtained one for the US movie event which was a special Toys R' Us event and the Darkrai would have been the ALAMOS one.
No, you must have Wi-Fi in order to do cloning. Or you can grab an action replay, enter the cloning code, and then clone as many versions of the pokemon as you want. But the way described in this exact thread, you MUST have Wi-Fi in order to do this, and it is in Diamond and Pearl only.