I seen one about the mimic octopus, they put it in a tank with a black n white chequred floor n it blended quite well
There was a documentary about it on BBC around the time they were doing those Deep Blue Sea and Weird Creatures documentaries. The octopus on there was copying every fish and the ray it came across. There was another octopus that changed its whole body in psychadelic colours really quickly that looked amazing - was like watching patterns on acid!
Why do people think that's fake? There are many creatures that can perform amazing things such as that!