A little girl wrote Depp asking if he'd come to her class to help "stage a mutiny". Well, Depp happened to be in town filming Pirates 4, and this is the result.
Very cool of him to do that for a fan. Not that this is the first time. A few years ago it was reported that he spent fours reading bedtime stories to patients at a hospital while dressed as Jack Sparrow. He had the costume flown in from L.A. especially to do this.