Welcome to PokéCommunity! Register now and join one of the best fan communities on the 'net to talk Pokémon and more! We are not affiliated with The Pokémon Company or Nintendo.
Ain't it something to do with the Pikachus in there? I think you play the pokeflute to get them near the egg, then hit them with food or something, they'll shock the egg and it will hatch. Atleast, thats what I remember doing, but I could be wrong.