Is there really a Pokemon named Arceus in the game?

No der you need the azure flutte when you are where you caught your diagla /palkia the flutte will start playing some stairs will apear the are the stairs to heaven arcues is up those stairs hes lv. 70 or 80 I think

Yes.

Yes there is. You have to first get the arzer flute, then go to the top of mt. Cornet where you battled dialga and blow the flute. Stairs will appere and climb them aand there is arceus.

Yes, there is a Pokemon named Arceus in the game. To get him, you must get, or receive the Azure Flute, then you must play it at the top of Mt. Coronet, or other known as Spear Pillar. Stairs will appear, go up them, and standing there, waiting for you is Arceus.

Hope this answered your question.

Yes there is but he is only obtainable through actioin replay.

Yes his the last Pokemon and theirs three ways of getting it
1. By Nintendo events
2. Action replay
3. Trading a friend that has it

Yes there is you can get it by an Action Replay or a nintendo event

Yes there is. But you have to have a azure flute to get him then go to were you got dialga or palkia and play it and I think hes at level 80 when you battle him. Hope this helps

Of course, Arceus is a major legendary Pokemon. Unfortunately it's an event-only Pokemon, but if you have an Action Replay you can get this Pokemon no problem. If you have an AR refer to AR codes in this section.
Good Luck. And Happy Gaming

Yes it's the number 493 Pokemon, last one in the pokedex.

Yup, Arceus is a rare legendary, you need the Azure Flute, only obtainable through cheating or Nintendo Events.

If you live in the UK, then I can say one thing. You're screwed.
The ONLY way to get your very own Arceus with your ID# and everything, without Action Replay, is to first obtain an item called the 'Azure Flute' basically you get that via Nintendo Event. Once you obtain the Azure Flute you take it to the 'Hall of Origin' (basically it's a floating glass-like platform above 'Spear Pillar', where you captured Dialga (Diamond) or Palkia (Pearl). When the stairway to the Hall of Origin appears, walks up the stairs. Save before you reach the top. Because once you reach the actual platform. There is no way back. Arceus will attack you and if you haven't got the Master Ball, he's a real pain to capture. Lv80, the highest level wild Pokemon in the game.
So basically, the other way to obtain an Arceus is to use Nintendo Wi-Fi Connection and get one through the GTS, although it'll cost alot, unless it's hacked.
Of course the sorta illegal-but-not-actually-illegal way of getting Arceus, is of course, Action Replay. And what fun s that? D=

Anyway, hope this helps ^.^

Yes there is

I haven't seen a question like this in a while. But yes, there is such a Pokemon. To get Arceus, you have to find it's code. When you put the code into your game using an Action Replay, go to any Pokemart. Except the Veilstone City Pokemart by the way. You will get an item called the Azure Flute. Take that to Spear Pillar (the top of Mr. Coronet). You then will encounter Arceus, which is at level 80. Arceus is also the highest leveled legendary that can be found in Diamond and Pearl.

Yes it is the last one

Yes there is. You have to first get the arzer flute, then go to the top of mt. Cornet where you battled dialga and blow the flute. Stairs will appere and climb them aand there is arceus.