You should try training basset hounds, they are very smart but also very stubborn and have little to no desire to please you!
I've seen octopus do some really odd things in captivity, I spent three years keeping them, from intentionally squirting water at me to get attention (they are very accurate too) to observing their excitement in getting an usual object to add to their fortress. They can open bottles, kill out of boredom-maybe even spite, show emotions through color changes, they are almost a never ending display of WTF! One of the oddest was crawling out of their tank through two other "freshwater" aquariums to get to their preferred food, live crayfish, and crawling back to their tank to feast on the crayfish. They are, IMHO, a lot like cats in their behaviors.
I'd really like to try cuttlefish someday, if anything they are even odder than octopus. Or bob tailed squid, I tried to have several bob tailed squid shipped from Hawaii back in 1978, the live coral arrived in great shape but the squid didn't survive. Those squid have light organs under their bodies.