ARCEUS … how do you even say that by the way… Ar-Ce-Us? Thats actually easy I guess… so anyways

ArCeUs will finally be available to catch in Pokemon Diamond, Pearl, and Platinum! All 3! So make sure you hit up a Toys R Us sometime between November 7th and November 15th. that’s 1 week.
If you have Platinum it will unlock a special event, just like it’s been for the last few events. I’m guessing Diamond and Pearl will have the boring “Pick it up at the pokemart” thing… well that’s the lazy way too.

So be sure to check that out!

serebii.net also reports trading Arceus into future Heart Gold and Sould Silver games will unlock special locations were you can obtain a Level 1 Dialga, Palkia or Garatina. Crazy ish.

1. You must have obtain the Pokedex from Professor Rowan in game.
2. You must have no more than two wonder cards. If so, then delete one.
3. You must make sure you have enabled the Mystery Gift option.
   1. Go to the Jubilife TV Center.
   1. Talk to the man who accepts messages on the second floor.
   1. Input Everyone Happy and WiFi Connection when prompted.
   1. Save your game.
4. At the start up screen, there Mystery Gift is now activated.
5. Under Mystery Gift, select “Receive Gift” and from “Via Wireless”.
6. Select “Yes” when prompted, and a wonder card will be downloaded.
7. Start a game, and make sure you have an empty slot in your team.
8. Go to any Pokemart, and talk to the deliveryman in front of the counter.
9. You will receive your new Member Card.
10. Make sure to save your game.

With the Member Card, go to the locked inn in Canalave City. Enter and sleep in the bed. Your character will fall asleep and wake up on New Moon Island. Explore the island to find a lvl 50 Darkrai ready to battle you. Make sure to save beforehand as this is your only chance.