When untamed, Emperor Penguins will act like any other mob. They will only spawn in snowy biomes. When attacked, all wild penguins around them will get mad and attack you back. Their call lengths vary based on how healthy they are.
When right-clicking any Emperor Penguin with a fish (raw fish, raw salmon, clownfish, or pufferfish), there is a 1/3 chance it will become tame, even if it is angry. Tame penguins will wear red bow ties. You can shear a tamed Emperor Penguin by right-clicking on it with shears. There is a 66% chance for it to drop 0-2 black or white Penguin Feathers, but a 33% chance that it will become angry and attack. However, other penguins you've tamed will not attack when one penguin is angry because you attempted to shear it. When a penguin is angry, it is possible to re-tame it with more fish. Attempting to shear a wild penguin will only make it angry. Note that tame penguins can be bred with wheat.
Upon death, Emperor Penguins will drop 0-2 black Penguin Skins.
1.6.2n: Changed animation when an adult is in the water. Now they swim horizontally.
1.2.5e: Adapted to match the new feather system. No longer attack skeletons. Can be bred using wheat if tame.
1.2d: Wing movements adapted to be more realistic.
1.1b: New look. Now drop skin on death rather than feathers. Can now be sheared for feathers.