Mimic Octopus

Not officially discovered until 1998, the Mimic octopus can change its texture, arm positioning, and movement, the mimic octopus is able to imitate around seventeen other animals, including lionfish, sea snakes, flatfish, and brittle stars.
Although all species of octopus have the ability to change the color and texture of their skin, and many species can blend in with the sea floor and look like rocks, the mimic octopus is the first octopus species ever observed to impersonate other animals.

http://en.wikipedia.org/wiki/Mimic_Octopus

http://marinebio.org/species.asp?id=260

http://news.nationalgeographic.com/news/2001/09/0920_octopusmimic.html