I think the usual thing is to go to Taronga Zoo, conveniently in Sydney. Instead I went to Featherdale Wildlife Park, a short train ride away, because I'd heard I could get closer to the animals there. Indeed, I'd have to be eaten by the animals to get any closer than I did.
The kangaroo enclosure overlaps with the human enclosure. Both we and they can get away from each other, but we have an area in which to mingle. Typically, humans carry more pocket change than kangaroos do and have better access to ice cream cones, so for 50 cents we get an ice cream cone full of kangaroo food (but no ice cream) and get to feed it to the kangaroos.
To add a little excitement, there are emu in there with us. Emu are curious, assertive, and seem to enjoy kangaroo food at least as much as the kangaroos do. Feeding birds in a park is a little less relaxing when the birds are as tall as you are and have (in the wild) been known to kick people to death. The emu photo here was taken over my shoulder while running away.
Koalas are woolly little beasts. There's a myth that they somehow get stoned on the eucalyptus leaves they eat, and watching them, it's easy to see how that rumor got started. I did see one scrambling around and hopping from tree to tree, so they can be nimble and lively, but most of the ones I saw were pretty dopey. I was still nervous about getting so close to those big claws, but I couldn't pass up the opportunity.
One bit of oddness, I mean in addition to all the freaky animals, was that the gift shop sold things made from the same sorts of animals that live there. Did you like the kangaroos? Buy a kangaroo skin purse! Did you enjoy the kangaroo, crocodile, and emu? Now available in jerky form! (I liked the emu best.)