The Drop Bear is a creature that appears only in Dumb Ways to Die 2 the Games.
Appearance
As implied in its name, it's literally (based on) the fictitious animal Drop bear, which looks very similar to the Koala.
Dumb Ways to Die 2 the Games
It appears in the Camp Catastrophe's minigame Drop Bear Woodchop where it falls on Loopy's head in the failure of the minigame.