Animals: Koalas, Kangaroos, Echidnas, Platypi (Platypusses?), and Tasmanian Devils are creatures that only inhabit Australia in the wild.
Seasons: Australian summer is most other countries' winter, and vice versa.
Land: Mostly desert and open plains. Probably contains the highest percent of desert of any continent (Antarctica is tundra, not desert).
This would also be a good nickname for Antarctica, which is literally under every continent.