Emu are the only birds with calf muscles.

What they lack in wing size (about the size of your hand) emus make up for with leg power! On top of the sheer size of their legs, a few special features help boost their strength. Emus are unique among all bird species, for example, in having a gastrocnemius. This powerful muscle, located on the back of the lower leg, forms part of what's known as the calf muscle in humans.

Emu feathers are like no other! Individual emu feathers have a loose and simple design. Just like hairs, feathers grow from follicles. Most birds have one feather per follicle, but the emu grows a double-shafted feather from each follicle. Barbs found on a typical bird feather are closely knit, but an emu feather’s barbs are widely spaced and don't have the usual hooks that attach to the other barbs. Instead, each barb hangs loosely and gives emu feathers a hairlike appearance. Other ratites share this feathery design. Emu feathers are less water-resistant than other birds' feathers. Its tail feathers are not so soft. Instead, they are stiff, and the bird can rattle them to scare off predators, such as dingoes. When shaken they sound similar to a maraca!

The Australian Emu (Dromaius novaehollandiae) has protective nictating membranes on its eyes. The membrane over each eye protects them from dust.

Nictating means blinking. The eye membrane is called a third eyelid, or a haw, or a plica semilunaris, or a membrana nictitans.   

A nictating membrane is a transparent or translucent eyelid. The eyelid membrane not only protects the eye from dust, it also moistens the eye and cleans away any dust or dirt. 

Normal upper and lower eyelids move up and down. The emu’s nictating eyelid moves horizontally, side to side, across the eyeball. It moves from the inside edge of the eye to the outside edge of the eye.