From Bulbapedia, the community-driven Pokémon encyclopedia.
About me
Hello, my name is Zander (well, not really, but my username is) and I recently got Diamond and am now in love with Pokemon and all the games except Red and Blue, because they suck.
I have only 3 games, Diamond, LeafGreen (which I messed up twice with AR) and Emerald.
Together, me and one of my friends have all Gen III and Gen IV games (enough to Catch 'em All) and
have almost all legendaries.
Action Replay
Yes, I have an Action Replay GBA. I only ever used it on LeafGreen, which is the game I use least.
Arceus
Ah, Arceus. The supposed God of Pokémon has yet to be released by Nintendo, and, being my favorite Pokémon, you can imagine I can't wait till they official release him. Currently, these are the (cheating) steps to get Arceus. I don't own a DS Action Replay, so I can't get him.
- Get the Azure Flute from the man in the Pokemart.
- Enter Mt. Coronet from either Route 208 or Route 207.
- Get to Spear Pillar. Once in the middle of the first platform, a message will appear, saying the Azure Flute is making a sound and will ask you if you want to blow into it. If you answer "Yes" it will play music almost identical to the Game Freak music at the intro.
- When the music ends, the screens will go white. It will then give you the message,
"A glowing staircase appeared!" and a transparent staircase will appear. The music will change into
music that sounds like the music at the intro when you see Dialga/Palkia's silhouette.
- I know this because I watched a video of someone doing it.
- Go up the staircase. When you reach the top, and step on to the first white square, a "!" will
appear above your head. Your character will walk forwards and battle the God of all Pokémon.
- After that, if you caught Arceus, you can check it's summary to find out the name of the place is the Hall of Origin.
And that's that.
Image:Hall Arceus.png
This user has a Shiny Medicham. 
