Mimicry in nature is common, where a species uses a pattern of another to exploit desired characteristics and increase its inclusive fitness. There are many examples, such the Hawk-cuckoo, a cuckoo that has feather and wing patterns like a hawk; the False Cobra, which has the same distinctive hood as the Indian Cobra; the African monarch butterfly, which is the subject of much copying due to its unpalatability; and very impressively, octopuses of the genus Thaumoctopus (such as the Mimic Octopus), which can change color and shape to resemble the poisonous lionfish or sea snakes.
There are at least half a dozen categories of mimicry in nature, some of which are much more common than others. There is Batesian mimicry, by far the most common, where a harmless species (the mimic) copies a harmful species (the model) to scare away competitors or predators. All the examples listed in the previous paragraph are Batesian mimics. Batesian mimicry works best when the mimics are in relatively low proportion to the model, otherwise the targets of the display eventually wise up to the imposter and treat it like the animal it really is.
Other forms of mimicry in nature include Mullerian mimicry, Emsleyan mimicry, Wasmannian mimicry, Vavilovian mimicry (mimetic weeds), Gilbertian mimicry (protective egg decoys), Browerian mimicry (one individual mimicking another of the same species), aggressive mimicry, reproductive mimicry, Pouyannian mimicry, automimicry (where one part of an organism resembles another part), and a few odd cases that do not fit into any of the above.
Mullerian mimicry is when two species, both with genuine defense mechanisms and associated aposematic signs (warning signs) come to resemble each other. This is common in butterflies and wasps. Looking like each other, they magnify the warning effect. If a predator or competitor has a bad experience with one, it will avoid all the others that look similar.
Emsleyan mimicry is a rare type of mimicry where deadly animals mimic prey items to lure in would-be predators, then kill them, turning the tables. This is believed to be the source of the Coral Snake mimicking the False Coral Snake and the Milk Snake -- though called "False," the False Coral Snake is actually the model and the Coral Snake is the mimic. By looking like a False Coral Snake, coral snakes can lure in hungry birds and dispatch them with their venom. This is one of the more original examples of mimicry in nature.