If you’re thinking McLeod, you couldn’t be further from the truth. What you have to do is think small; not microscopic, just big enough to see with your naked eye. Turritopsis nutricula is a hydrozoan, and it’s considered by scientists to be the only animal that cheated death.
Solitary organisms are (according to current belief) doomed to die, after they completed their life cycle. But Hydrozoa don’t live by normal rules. Nope, Hydrozoa are a huge class of predatory animals that live mostly in saltwater, closely related to jellyfish and corals. Eggs and sperm from an adult jellyfish (medusa) and they then develop into polyp stage. Medusae evolve asexually from polyps.
Still, our Turritopsis nutricula (can I call it Joe?) managed to find a way to beat that. What these little folks do is they revert completely to a sexually immature, colonial stage after they reach sexual maturity. They’re even cooler than that. When they’re young they’ve got only several tentacles, but at a mature stage, they get to 80-90 of them.
They’re able to return to polyp stage due to a cell change in the external screen (Exumbrella), which allows them to bypass death. As far as scientists have been able to find out, this change renders the hydrozoa virtually immortal.
Edit: This species is now classified as Turritopsis dohrnii – but since I wrote this article, biologist changed their mind and gave it a new name and a new classification. Everything else remains the same though.