Emus are a species of bird native to Australia. In the Polandball comics, Emus sometimes make appearances as a subject of the Emu War or upon the mention of dangerous animals. They don't kill anyone and are very peaceful animals BUT they are very hostile to Australiaball.
He attacc | He protecc | But most importantly, he pecc
Despite Emus' hostility to Australiaball, the Emu (along with the Kangaroo) are both in the Australian coat of arms.
Rabbits - They helped the Emus win the Emu war. And frankly they like pissing off Australians as much as Emu's do
Cassowary - The Emu's more dangerous brother. Responsible for killing more Australians than the Emu.
Kangaroo - Emu's best mate. They are seen together in the Australian Coat of Arms.