And while no-one has been recorded seeing a platypus hatch, it's thought they look like a gooey, furless echidna hatchling. The baby platypus is born around 1.5 centimetres long but rapidly grows ...

Now, whether this factors in the size of the fedora worn by the most famous platypus in history, Perry the Platypus from Phineas and Ferb, is unclear – though it likely wouldn't make a difference.