Quote Originally Posted by Bulbapedia
Secret Key to be available in North America

To be distributed via Wi-Fi and Toys "R" Us stores

The Secret Key will be available over Nintendo Wi-Fi Connection and at Toys "R" Us stores in the US, Canada, and Puerto Rico. They will be available via Wi-Fi from April 20 to May 12 and at Toys "R" Us stores from April 19-26. The gift is only available to players of the North American version on Pokémon Platinum. Mystery Gift will be utilized in both distributions. The Wonder Card obtained from the event can be shared to five other players of Platinum who have not received card.

The Secret Key is used to change Rotom to its other forms in Platinum. The player must have cleared the Galactic Eterna Building for the key to work.
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Sooo, who's gonna do this and in what matter? Me and my Dad are gonna do it via the TRU route.

We gotta activate Mystery Gift in our games, though (I already know how).