Well, if you're getting into rock, you gotta be prepared with "Free Bird"! ;-}

There are a slew of Flanders and Swann songs about animals, including the platypus. My favorites are about the gnu (of course), the sloth, the kangaroo and the jaguar.

I was going to recommend "The Kangaroo Song" ("A kangaroo sat on an oak"), except it involves kangaroo hunting and Cheneyesque porcinicide--not quite fitting for the intended venue.