I had a small octopus back in the day (1980-81), caught it myself and brought it back from a trip to Puerto Vallarta, Mexico. Not too sure of the legality of that, either then or now, but we brought small fish/inverts back regularly on our Mexican vacations back then without any questions asked or info volunteered. The octopus lived in a 50-gallon tank loaded with lava rock, some live rock (guess where that came from?) and with a heavy growth of Caulerpa macroalgae; no corals, fish, crabs, etc. Aside from the tiny worms and critters on/in the rock he was always kept alone.
We were not sure what Thing's exact species was, and with only the one specimen at hand, we weren't certain of sex either. One of his arms was indeed different than the others, indicating a male...but it was not really matching the descriptions in the literature so we simply weren't sure. No internet to allow easy research. I always related to Thing as a male; my wife insisted he was a she.
Thing (named by my wife) would curl up in one of the ceramic pots I provided as a home, and watch me as I watched him. If I moved my chair, he would sometimes slip into another pot that allowed a better view of me...but more often he would just reach a couple of arms out through the opening and turn the pot around to be facing me squarely. If I presented a food item in tongs and held it just within reach, he would extend one tentacle out and grasp the food to pull it back into his lair. If I held fast and didn't release the item, he would tug and pull a bit, then extend a second arm to increase his pull strength. If I still held fast, he would eventually start dragging himself, pot and all, towards the food...but he didn't like that so he would grasp a nearby rock or other support with a couple of arms to brace himself in place and pull all the harder. And when he still couldn't pull the food away from me Thing would finally lose his cool and just launch himself out of the pot and envelop the item on the end of the forceps. All of this would be accompanied by the lightning fast colour and pattern changes indicating his various moods.
Thing was mesmerized by TV; the three of us...me, my wife, and the octopus...would have quiet evenings of just sitting watching the tube. You could almost see which of us was thinking the hardest about the show...hint: it wasn't me.
Thing didn't care for music, and would pout and flash angrily if the speakers played much more than whisper-loud; I actually moved my stereo into the den so as to make the octopus more comfortable in the living room.
Thing absolutely loved teasing my cat (yes, in those benighted condo-dwelling days...I had a cat rather than a dog...). He would sit and watch Max as Max watched him; if Max started to turn away or lose interest, Thing would wiggle an arm to capture his interest again. You could practically hear Thing thinking: "You are much bigger than I am...but I am sooooo much smarter than you...."
I often got the impression that it thought the same thing about me. My wife was absolute positive about it.
We would pick up toys for our pets when we visited pet stores. For Thing, toys were carefully examined and tested for toxicity and other safety concerns before being presented to him. For Max? "Ah, that'll be fine..." The octopus was treated like a precocious only-child...spoiled rotten.
When that animal died a bit over a year later, both my wife (girlfriend, then) and I were devastated. It was much closer to losing a dog or cat rather than "just another fish". After the experience of keeping Thing, I could never consider any type of fish a proper "wet pet" because there is literally no comparison. People who tend to discourage anthropomorphism...and I am such a person!...would find it difficult not to indulge in that with an octopus. It was at once the most rewarding human/animal interaction I have ever experienced outside of dogs and cats, and it was over way too soon; would never wish to repeat that.
