Parasitic wasp Larvae
Parasitic wasp larvae are nature's worst guests ever. They can lay up to 80 eggs a time in caterpillars and once hatched, they feed off the caterpillar's bodily fluids before eventually eating through its skin. The ichneumon wasp shook Charles Darwin's Christian faith more than anything else he encountered writing On The Origin Of Species:
I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of caterpillars.
The horror frog
Surinam sea toads give birth through holes in their backs, in a process which looks as bad as it sounds and is virtually guaranteed to make your skin crawl.
Spotted hyenas have super-strong stomachs and have been known to eat anthrax-ridden animals without suffering any ill-effects.
Sea cucumbers are starfish-like creatures. If under threat, a sea cucumber will expel its internal organs through its anus. The missing body parts are then regenerated.
Turkey vultures have an odd method of self defence - vomiting. If under attack the birds - also known as turkey buzzards - will regurgitate semi-digested meat in an attempt to put off predators through smell.