I love my roos for the sense of calm and silliness they bring me. I would love to have new sounds pop up occasionally. The first time I got a purple lollipop was the day I coaxed out my first koi so for about an hour I thought that the Koi's dropped lollipops. It gave me a whole new, if wrong, thing to investigate with my roos.

Adding a new sound, maybe to just one species or another, would add a new element to something that many of us have become immune to. That being said I have no idea how to accomplish the programming and how hard it would be.