On Caspian's Unbirthday, his grandpa always gives him a silly present that just isn't right for a birthday present. This year it's brown underpants. Caspian is disappointed. Grandpa calls them "Hot Chocolate Underpants," and spills cocoa on Caspian's lap. Caspian glares. Grandpa smiles. Then Caspian's butt twitches. The humorous adventure begins with flying, using a broom and a mop to steer.