The mimic octopus lives in the sea near Indonesia. It can change its shape and the way it moves. It can look like a flatfish, a lionfish, or a sea snake. Some people say it can copy thirteen animals, but this may be too much.

Scientists watched the octopus for a long time. Most often, it swam like a flatfish. It did this when it moved across open sand, where fish could see it easily.

Most octopuses hide during the day, but the mimic octopus of Indonesia walks openly across sandy sea floors in daylight. In 2001, Mark Norman and his team described nine of these animals changing their arms and movements to resemble a flatfish, a venomous lionfish, and a sea snake. When a small fish attacked one octopus, it took the shape of a sea snake, which is an enemy of that fish.

Later, however, Roger Hanlon's team filmed the octopuses for five days and recorded about 500 cases of flatfish mimicry. The octopus usually stayed hidden by matching the color of its surroundings, but when it had to move, it pretended to be a flatfish, a common animal on the sand.

In 2001, Mark Norman and colleagues described an octopus that seemed to impersonate other animals. Nine individuals took on postures resembling flatfish, lionfish and sea snakes. One octopus, harassed by a damselfish, displayed a sea-snake shape, and the researchers wondered whether it chose its disguise to match the threat. The animal had first been noticed in Indonesia in the late 1990s and was formally named Thaumoctopus mimicus in 2005.

Its fame grew quickly, and popular accounts later claimed it could copy thirteen species. Roger Hanlon's team took a more careful approach. Over five days of filming, they recorded about 500 episodes of flatfish mimicry and concluded that the octopus mainly relies on ordinary camouflage. It switches to a flatfish disguise when moving would otherwise make it conspicuous.

When fish actually bothered it, it used standard octopus defenses such as ink and escape. No experiment has yet checked whether predators are fooled by the lionfish or sea-snake forms, so the idea of threat-specific mimicry rests on anecdotes. There is also a human factor. Deciding which animal a twisted posture resembles may depend on who is looking.