So... I've never actually attempted to capture a Pikachu that held a Light Ball, so I'm not particularly sure it wasn't possible in b/w and b/w2... But I caught one by accident. ( And immediately pondered my luck, and asked myself, in a tearful manner, why I received a lightball Pikachu, but haven't been graced with the blessing of witnessing the beauty of a wild shiny since Gen 3.. )