Here is a quote from serebii.net:
In Battle Revolution, after completing the game, you are able to get a Surfing, Volt-Tackling Pikachu. Well, this is not the only Pokémon you can get off of Battle Revolution. You can also get a special Electivire & Magmortar, Pokémon that may be hard for you to get in Diamond & Pearl if you do not have previous games.
To get these Pokémon, it is a simple method. First, you will need to go in and go to edit your profile
From here, go into your Self-Introduction. This is where you will need to input your details normally for the start of battle
In there, you need to input a certain thing, one for Electivire and one for Magmortar. Unfortunately, I am currently unable to reveal to you the actual data required for input for you to do this, once I can, they will be here. Once they are in, save and exit the profile entry
Once the correct codes are entered in and saved, the lady at the desk shall note that you have entered in the secret password. She will go on to explain that you have unlocked the Gold or Silver Pass and that the Shocking or Heated Secrets have been added to the Mystery Gift shop for Electivire & Magmortar respectively.
Now go into the in-game shop and at the bottom of the list of items you will find the Heated Secret Gift or the Shocking Secret Gift depending on what you entered. They are at 0 PokéCoupons in price such as with Pikachu so you won't have to shell out any of your hard earned PokéCoupons.
Once you've selected them, the usual Mystery Gift sending procedure comes up. You can now send Electivire or Magmortar to Diamond & Pearl. You can only send it once to the game so be weary.