What is the scientific name of the australian animal that drastically changes its appearance?

The Australian animal that drastically changes its appearance you're likely referring to is the Giant Cuttlefish, whose scientific name is Sepia apama.

While many animals camouflage, the Giant Cuttlefish's ability to rapidly and dramatically alter its skin texture, color, and pattern is exceptionally sophisticated. This allows it to blend seamlessly with its environment, both for hunting and avoiding predators. The changes are not simply variations in a few shades; they involve complex displays of vibrant colors, intricate patterns, and even the creation of textures to mimic the surroundings, like rocks or seaweed.