Found on Facebook today - putting it here, not in the (as yet unstarted) research threads because I haven't checked it, but if it's true I love it.
Not only do wombats have square poo, they have an armoured butt.
When pursued by predators a wombat will run back to its den and plug the entrance with its butt. A wombat's butt is covered in thick cartilage, which is quite scratch and bite resistant, and most wombat predators can't get through it.
If a predator manages to stick its snout into a wombat's den, the wombat will use its powerful back legs and its padded butt to crush the predator to death - i.e. it literally twerks predators to death.