XOk this question is for ChoasBug7. He said the event items and the places..

Glad you asked. In order to get these items, you eiter have to get them at a nintendo event. (None are being held in the US yet.) You must go to these events in order to obtain these items. I never had luck with Mystery Gift, but others have in geting these rare items. The people who already own them either cheated, traded over the GTS for one, Mystery Gifted them, or went to the Event held in Japan. As for the Action Replay, there are codes on this web site that do work. This is how I obtained Darkari, Shaymin and Arceus. To enter the the code, there is a section in this site where people post codes they know. Here is how to type it in manually. I will use the Darkrai event as the example. Credit goes to Poke8111
First you will need to create a new code list for Pearl if you haven't already. The pearl ID is APAE-31D0AFDE.
Next, go to add new code. Type in the a name for the code. Darkrai Event works well for this cheat. Name it so you have a clear understanding of what it does. Hit next with the stylus or your finger and begin typing the code in. Here is the Darkrai code as my example. P.S. This one does work.

94000130 FCFF0000
B21C4D28 00000000
B0000004 00000000
0000AA3C EDB88320
2000AA68 00000008
D2000000 00000000

Hit next and it should be in your list. Many codes posted work on Diamond and Pearl. Now just checkmark the code you want to use and hit the start on the DS. When ingame, hit L and R at the same time and enter a pokemart. A guy in a green coat will be standing there is the cheat is done right. He will give you the item. That's all there is to it. Just a warning, do not use all of the cheats posted, some can really screw up your game,or don't work at all, so always be cautious of what you use.

You go to the event and they give you the thing to get the Pokemon in-game.