Ninja are common stock characters in both Japanese and international popular culture. Depictions range from anywhere between realistic to fantastically exaggerated.

Ninja characters are often identified by their use of traditional bladed and ranged weapons in modern and even science-fiction settings, as well as numerous inhuman abilities such as running on water and up walls. Though depicted as nearly-invincible warriors (especially when they are the heroes of the story), they are often conversely depicted as disposable cannon fodder to be dispatched by the hero. Ninja are also often a subject of parody.

Source: Wikipedia