you can't
You can't without cheating. Sorry
no you cannot. unless you go to the special events Nintendo does.
The action replay is a device used for cheating.
Arceus is a future Event Pokemon. It has not been officially released at a Pokemon Event yet, but eventually it will come. Well, if you consider an action replay not cheating then that's another way.
There is a way to do it without cheating. Just simply trade a Pokemon that knows fly. Example: you have a staravia in Pokemon pearl that knows fly. Just trade it to Pokemon diamond.
you had to have gone to the event a couple years ago so u can only get it by cheating now
Cheating with Action Replay. Go to a Pokemon event! - by imaier Cheats, trading, or migrating
You can cheat on Pokèmon by play either Pokèmon Pearl or Pokèmon Diamond, then you'd be cheating on Pokèmon Platinum =)
Action replay
you can get to all islands without events to get the three remaining legendaries are paticipating in an event not possible anymore or action replay, cheating and glitching with the game.
No
no you have to get is from an action replay or go to a Pokemon event