Billions of years of evolution and more than 1 million species of animal have created very weird world and some very bizarre body parts. From sex-crazed slugs to Kung Fu crustaceans, from blood-firing lizards to zombie snails, we journey from the ocean depths to deserts and tropical rainforests to reveal that for some creatures, the truth really is stranger than fiction. We showcase some of the strangest, most shocking animal appendages on the planet, and uncover their evolutionary advantages.