I don’t want to be that guy who just recycles whatever is out there for you to find on the internet anyway, so I’d just like to draw your attention to this site which lists some of the more fascinating aspects of this creature.
Now, whether you’ve bothered to click on that link or not, if you ignore the picture above for a moment and just imagine that you are an early discoverer of this amazing little beast. Your description of it would have to go somewhere along the following lines. In this scenario you are person A, and person B is the uninitiated person with no idea what a platypus is:
A: Hey. You’ll never guess what I’ve just discovered.
B: A Yowie? Quick, contact the YRDB!
A: Nope. Better.