Member Card
The Member Card (Japanese: メンバーズカード Member's Card) is a key item available in Pokémon Diamond, Pearl, and Platinum. It is only obtainable through a Nintendo Event. The Member Card allows players to travel to Newmoon Island, where Darkrai can be obtained.
From December 1, 2008 to January 15, 2009, players of Pokémon Platinum can download the Member Card over the Nintendo Wi-Fi Connection. Unlike the Secret Key, the Member Card cannot be shared.