A long time ago a tribesman called Junbung was responsible for looking after his tribe's firesticks and making fire when it was required.  One day he decided to make a fire, so he took one of the firesticks and blew on it.  He was expecting sparks to fly off and light the tinder.  Instead the sparks turned into gold before they landed.  He blew the firestick again and the same occurred.  He know got very excited about the idea of making gold, so he started to blow and blow.  Eventually the heat that he was generating  caused his mouth to become very hot and swollen.  It got to uncomfortable for Junbung that he ran over and jumped into a nearby river to cool down.  There he stayed, eventually turning into the platypus.