According to the official website, European players of Pokémon Diamond, Pearl and Platinum will be able to download the Pikachu-colored Pichu, essentially a shiny Pichu, into their games between March 5th and March 25th. It is currently unknown whether this event also applies to the rest of the world. The event is confirmed to work on American and Australian games as well.
If you don’t know how to download this Pokemon, check our detailed instructions and your game’s booklet on how to setup the Nintendo WiFi Connection.
This special Pichu, when traded to forthcoming games HeartGold & SoulSilver, will allow the player to access the elusive Spiky-eared Pichu.