your annual octopus

lvl 2: the plural version of octopus is octopi because if a word ends with "us" the plural version replaces the "us" with "i" e.g. cactus -> cacti and fungus -> fungi

lvl 3: actually, that rule is only for latin words. octopus is a greek word and the correct plural is octopuses or octopodes

lvl 4: actually, language is descriptive not prescriptive. since enough people over time have used octopi as the plural for octopus, it's a valid plural

Octopuses and pillow lava—two of our favorite things 🐙🌋⁠

A Day Octopus, scientifically known as Octopus cyanea. 

All this is to say that the fact that this octopus appears to be dreaming means one of two things. Either

a) dreaming is a very, very old thing indeed, going directly back to the Urbilaterian. This would mean that almost every animal, from insects to starfish to sea slugs to newts, is likely to have the ability to dream in some capacity or another (unless they have specifically lost it by evolutionary simplification).

or

b) dreaming evolved entirely independently in cephalopods when they developed greater intelligence. This would suggest, at least, that there’s something very fundamental about dreaming related to intelligence itself, which causes it to emerge independently when sufficient intelligence arises.