This is amazing. The fish is imitating a mimic octopus; in other words, it's a fish pretending to be an octopus that pretends to be a fish:
The Mimic Octopus (Thaumoctopus mimicus) is a remarkable imitator, apparently assuming shape and behaviour similar to models as diverse as poisonous Lionfish, Soles and Sea Snakes (Norman et al. 2001). All of those models share in common stripped brown and beige or black and white colour patterns. During a diving trip to the Lembeh Strait (North Sulawesi, Indonesia) in July of 2011, the third author filmed a Mimic Octopus for about 15 min and recorded an unexpected relationship: the Black-Marble Jawfish (Stalix cf. histrio) followed the Mimic Octopus for several minutes, remaining very close to the octopus’ arms (Fig. 1; Electronic Supplemental Material). The colour of the Jawfish matched the banded pattern and colour tone of the octopus.
It's kind of like Turkish politics. The AP's reporting on the latest is accurate, by the way, for those of you who like to keep track of the arrests.