Toys R Us is distributing Ash's Pikachu at it's stores from January 30, - February 5, 2011.
Bulbapedia is speculating that Ash's Pikachu will likely be the same as the Ash's Pikachu already released in Japan - a level 50 Pikachu in a Cherish Ball with a Classic Ribbon, holding a Light Ball. Ash's Pikachu would have a Naughty nature, and the moves Volt Tackle, Thunderbolt, Iron Tail, and Quick Attack.
Everyone with a 4th generation game (Diamond, Pearl, Platinum, HeartGold, & SoulSilver) will be able to get Ash's Pikachu.
Link to the Toys R Us announcement:
http://www.toysrus.com/shop/index.jsp?categoryId=4311963 Link to the Bulbapedia News post:
http://bulbanews.bulbagarden.net/wiki/Toys_%22R%22_Us_to_distribute_Ash%27s_Pikachu All the credit should go to Bulbapedia, since that's where I found out about the TRU giveaway.
Since Ash's Pikachu is so close to the Legendary Crown Beast Giveaway @ Gamestop, you will probably have to soft-reset one of the Legendary Beast to open up a Mystery Gift Slot (I will be soft-resetting Entei).
I'm still hoping for a Celebi giveaway.