According to this Nature.com article, "Two tiny species of tropical octopus have demonstrated a remarkable disappearing trick. They adopt a two-armed 'walk' that frees up their remaining six limbs to camouflage them as they slink away from trouble. . . . Instead of its usual sprawling crawl, O. marginatus fled from divers by striding on two arms, with the rest of its arms wrapped around its body, giving it the appearance of a walking coconut."
The article includes video of the walking octopus.