One morning there's a knock at JoeÂs door. ItÂs Osbert the penguin. HeÂs escaped from the zoo, and he and his friends (all twenty-one of them) want to travel to Antarctica for a once-in-a-century spectacle: the southern lights. Luckily Joe has a helicopter, for everyone knows that penguins canÂt fly. But when they land at the South Pole and pile out to watch the skies, it seems Osbe…