A few years ago, there was an aquarium lab somewhere with fish tanks with live specimens in them. They had this one tank that fish were mysteriously disappearing from, and they couldn't figure out why. They eventually suspected an octopus in a tank nearby. They set up a camera, put some fish in the tank, and left for the evening. Next morning as usual, they found the fish tank devoid of any fish. They watched the video and sure enough, at night the octopus would crawl out of its own tank, slither down the stand, across the floor, climb up the other stand and into the tank to eat all of the fish. The weird part was, he would then climb out of the fish tank and return to his own tank. They wondered why the octopus didn't just stay in the tank he just cleaned out.
Sly critters they are.