The stonefish, an incredibly venomous fish living in tropical waters mostly off the coast of Australia and parts of US, can cause pain that only escalates with time. Without antivenim or denaturing the venom with excessive heat, the pain builds and builds until the patients request euthanasia. Its spines hold the venom, hidden in its dorsal fins.
Aboriginals living around the Great Barrier reef have "corroborees," large gatherings, and will during these gatherings hold reenactments of people being stung by this monster (for what I assume is either amusement, learning, or both).
Edit: corroboree clarification
It was once discovered that a fir tree was growing inside a human body. Artyom Sidorkin went to the doctors suspecting something wrong with his lungs. The doctors thought they were dealing with a tumor but turns out he had inhaled a fir tree seed which had sprouted and had begun growing in his lungs.
Edit: Wow so Greys Anatomy is a popular show. Im sure this was the inspiration for that episode.