http://www.bbc.co.uk/news/science-environment-25185236
I just thought this was pretty cool - apparently Koalas have extra throat flaps outside the larynx which is why they can make really low noises. :)
Because I'm feeling massively mature, I'm not going to post a post which insinuates that australian scientists discovered this whilst doing something unspeakable to the koalas throats. Just so you know.