On Marona's island there's a large tree next to her house. You must toss four people onto the tree and have them stacked on top of each other (You can get on the roof of the house by jumping on the back deck and from their jump on the roof). From there, jump up the stack of characters and once you reach the top character, jump one more time and you'll receive a message saying you got the Bottle Mail character. You'll also receive some cash and a Change Book for jumping that high.