I visited the obligatory zoo when I was in Cairns. I missed the Steve Irwin Australia Zoo, which is spoken highly of in The Lonely Planet, so I was overdue. It felt like a small zoo, however given all the animals felt exotic, I easily spent 3 hours there (in the 95 degree heat).
I caught the snake show, which featured the world's most venomous snake (the Inland Taipan). Michael said the hill they lived on was crawling with them, though they'd never seen one (just pythons that stretch across the street, among other creatures!).
Cuddling a koala bear was a mandatory photo-op!
And of course I had to watch the crocodile feeding. Sarge was a monster of a croc!