Ninja Kid, known in Japan as GeGeGe no Kitaro - Youkai Dai Makyou (ゲゲゲの鬼太郎 妖怪大魔境), is an NES game developed by TOSE and published by Bandai. The Japanese version was based on the manga series GeGeGe no Kitaro, but the game was changed to the generic "Ninja Kid" and all reference to Kitaro were removed for the American version. This game was followed by a sequel titled Gegege no Kitarou 2: Youkai Gundan no Chousen, which was released the following year only in Japan also by Bandai; however, this game was an RPG and its plot is unrelated to the original.
Gameplay begins on an overhead map with several different arches. Each arch leads to a different side-scrolling mission, and the type of the mission can be determined by the shape of the arch. At the end of each mission, two doors will appear, one of which will return to the map, and the other of which will take to a vertically-scrolling tower with a mini-boss at the top (after defeating the mini-boss you are returned to the map). Also during each mission, items randomly appear on the screen. Some bonus items also give a temporary speed boost, or an owl that shows you which door leads back to the map (instead of the mini-boss tower). Once collected a scroll, it can be taken to the hut in the middle of the map to unlock the fortress and fight the map's boss. During the boss fight, if any whistles have been collected , the character can crouch in the far left corner of the screen to use a whistle to summon a familiar.
The original Japanese version is notably different from the American version. The main character is Kitarō, and his main weapon is his hair rather than darts. His sub-weapons are a flying finger instead of shuriken, his vest instead of the feather, and a geta instead of a boomerang. All of these weapons function the same as the ones of the protagonist of the American version, Kyo; they just use different sprites. The fireball sub-weapon remains the same. Somewhat bafflingly, one level is inhabited by "western" film monsters like Frankenstein's Monsters and Count Dracula; the boss of said level is a Buckbaird. The scroll which unlocks the fortress is a crystal ball in the original version. The familiars are also different, being characters from the manga: the Pegasus was originally Nurikabe, the Eagle was Konaki Jiji, and the Mirror was Sunakake Babaa. Finally, a few of the minor enemies are different; most notably the "Pirate Ninja" found in some of the Guerilla Warfare levels was originally Nezumi Otoko, and Kitaro rides on Ittan Momen during the Dog Fight levels.
Source: Wikipedia, "Ninja Kid", available under the CC-BY-SA License.