The octopus is a magnificent and mysterious creature. They’re well known for their eight tentacles, but did you know these other outstanding facts?

1. "OCTOPI" IS ONLY KIND OF THE PLURAL FOR OCTOPUS.

Need a name for your friendly neighborhood group of octopi? Octopi might not be the word you actually want. It came from a time when grammarians tried to regulate English to have similar endings to Latin. Other options include "octopuses" (which is the choice of the AP Stylebook, the guide that dictates grammar rules for most journalists) and "octopodes."

Kory Stamper, a lexicographer at Merriam-Webster, breaks it down below.

2. THEY’RE SUPER SNEAKY.

As we’ve written about previously, scientists think octopuses are colorblind, but that doesn’t stop them from instantly camouflaging themselves when necessary. Matching the colors of the seabed or algae-covered rocks is no issue for them. What’s more, T. mimicus has been known to make itself look like other, much more dangerous creatures by changing shape. Just watch ...

3. THEY LOVE PLAYING WITH TOYS.

We wrote about the time an octopus broke into a library to read some books. They’ve also been known to play with rubber duckies, LEGOs, and even a diver’s camera. They’re often drawn to shiny things or objects they haven't seen before.

4. THEY’RE GREAT HOMEMAKERS.

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Octopuses find homes wherever they can, from bottles to shipwrecks. They’re known to move often in order to follow sources of food, but if they have a more permanent pad, they’ll put shells and other objects in an "octopus garden" outside to decorate.

5. THEY'D HAVE NO PROBLEM TAKING YOU DOWN.

Usually, a human's interaction with an octopus wouldn't be much worse than getting some water squirted at you (as this guy learned). That being said, some people used to like a challenge, so they went big—octopus wrestling-big. Yes, in the middle of the 20th century, octopus wrestling was a very real thing. There was even a World Octopus Wrestling Championship. But Washington State quashed the games in 1976 with a law that made it illegal to “harass” an octopus. Because of that, you probably shouldn’t expect the sport to make a comeback.

6. THEY GET SPECIAL TREATMENT.

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In the eyes of the law, anyway. In 1986, the United Kingdom passed ASPA—or the Animals (Scientific Procedures) Act—which severely restricted which animals could be used for research. The law included protections for “any living vertebrate other than man.” In 1993, they passed an amendment that would extend the law’s protections to “any invertebrate of the species Octopus vulgaris from the stage of its development when it becomes capable of independent feeding.” Many people cite their intelligence as evidence that octopuses are worthy of the exception.

7. THEY EAT OTHER OCTOPUSES WITH SHOCKING REGULARITY.

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If they’re hungry enough, an octopus will eat a younger member of its species. (A team of researchers even caught it on video for the first time last year.) Scientists have also observed a female octopus eating her mate after they did the deed.

In order to avoid being killed after copulation, male octopuses have special adaptations to help them. These include mating at arm’s length, special disguises, and even occasionally sacrificing a limb.

8. BUT SOMETIMES THEY DON’T KNOW WHEN TO STOP.

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What is worrying to some scientists is that the cannibalism isn’t always limited to other octopuses. Some octopuses have started eating their own limbs and then dying, which scientists originally chalked up to autotomy, a behavior in which an animal will break off a limb for self-protection. The animals would die soon after doing this, and others that had been near it would start doing the same thing.

Stress or boredom both could have caused the problem, but eliminating sources of either didn’t make anything better. Some now believe it could be a disease attacking the nervous system that’s causing this strange behavior.

9. SOME SCIENTISTS BELIEVE THEY HAVE PERSONALITIES.

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Through testing, scientists have found that individual octopuses respond differently to situations. This implies that, like humans, each octopus possesses individual characteristics.

10. EARLY RELATIVES MAY HAVE BEEN AROUND ALMOST 300 MILLION YEARS AGO.

Now resting at the Field Museum of Natural History in Chicago, Pohlsepia is the octopus’ oldest ancestor. Like an octopus, it lacks a shell and has eight arms—the first creature to do so. It was found in the Pennsylvanian Francis Creek Shale of Illinois' Carbondale Formation.

11. THEY HAVE SPARKED MANY SEA MONSTER LEGENDS.

The octopus probably sparked ideas of the Kraken, the akkorokamui, and more. When a ship was lost at sea, many people just accepted that the Kraken probably got a hold of it and that they likely wouldn’t see their loved ones again.

We first started drawing the Kraken as gigantic octopuses sometime around the 18th century (it started its life a little more crab-like) and the imagery has stuck—even though every example of the Kraken has now been debunked. The St. Augustine Monster, a creature that many thought could have been an unknown species of huge octopus we hadn’t yet discovered, later turned out to be parts of a definitely-discovered whale.

12. OCTOPUSES DON'T STICK TO THEMSELVES BECAUSE THEY CAN'T.

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Each one of an octopus' tentacles operates completely independently of the body as a whole, yet they don't get tied up in knots. How? It's been discovered that octopus tentacles can stick to everything except octopus skin, meaning that the creature is safe from itself.