This right here, explains the whole scene when Harry dances with Hermione. It's actually one scene that wasn't in the book that I absolutely loved in the movie, 'cause it showed how much Harry really cares about Hermione as one of his best friends.
Thank god someone invented this! If there is one thing that drags me down in life and ruins nearly every party, it is having to lift a 2 liter bottle of soda to pour. A bottle brings you down in life! Must be a tough life!