Things You'll Need
Instructions
Load your "PokéPark Wii: Pikachu's Adventure" save game file. The main menu appears. Select "Password."
Enter the password "65967413." A confirmation message lets you know that you unlocked Darkrai.
Go through the gate on the right side of the central hub to enter Haunted House Zone. You arrive in the courtyard. Go straight to enter the haunted house.
Run straight to enter the house's back room. Darkrai floats around in this room. Talk to Darkrai and select "Yes" when he asks you for a battle.
Charge into Darkrai to damage him, or use Pikachu's Thunderbolt attack. When Darkrai's hearts disappear, you win the battle.