I hadn't, until I came across an article about the species on Geekologie. According to Wikipedia, the mimic octopus was only discovered in 1998. Its main claim to fame is that it imitates, or mimics, a large number of other species, some of them deadly poisonous, as a way of either camouflaging itself against detection, or intimidating potential enemies into leaving it alone.
Here's a fascinating video about the species.
Call it God's creativity, or evolution in action, or what have you . . . but isn't Mother Nature amazing?