Duck-billed platypus

Ornithorhynchus anatinus

One of my all-time favourites, for its complete and utter oddness. Its bizarre appearance – looking part-duck, part-beaver and part-otter – meant that the first scientists to observe one thought they had a hoax on their hands. Despite being a mammal, the platypus actually lays eggs and is one of only five types of mammal to do this.