The closest animal to an alien is an octopus.
Octopus's are very widely considered to be the most alien like animal on Earth.
Octopus's evolutionary lineage split from ours millions of years ago, which gives them completely foreign physical and also genetic traits.
The outerworldly features of the octopus includes having 3 hearts, blue blood decentralized brains and scrambled DNA.
Octopus's have over 33,000 protein coding genes, which is roughly 10,000 more coding genes than humans.
Octopus's can also edit their own RNA, allowing them to rapidly alter their nervous system to survive changing ocean temperatures.
An octopus also has decentralized brains, which means that octopus's have 9 brains in total.
The central brain of an octopus, controls the body, and a mini brain in each of the octopus's 8 arms, which allows their limbs to taste, touch and operate independently.
Octopus's also use a copper based protein called hemocyanin to transport oxygen, which also works efficiently in cold deep water.
And as for the 3 hearts that the octopus has, 2 hearts in the octopus pump blood to the gills, while the 3rd heart circulates the blood to the rest of the octopus's body.
An octopus is a highly intelligent, soft-bodied marine mollusk of the order Octopoda.
Famous for their eight arms lined with sensory suckers, octopuses lack skeletons, allowing them to squeeze through tiny crevices.
The octopus is also remarkable for possessing three hearts, blue blood, and the ability to instantly change skin color and texture.