They are keychains given to customers at Toys R Us who purchased LEGO Harry Potter video games on their release date. Four were available, two upon reservation, and two more upon pickup. The HP graphic design is only a sticker on this ['Tile 4 x 4 with Studs on Edge' (6179)] piece in white with a chain attached.
There is no life I know to compare with pure imagination. Living there, you'll be free if you truly wish to be. -Willy Wonka, 1971-