Mazinger Z (マジンガーZ or マジンガー・ゼット), also known as Tranzor Z, is the name of a manga by artist Go Nagai, first published in Japan in 1972, and turned into a long-running anime television series later in the same year. The series lasted for 92 episodes, making it the longest running anime mecha series in the genre. It remains the stepping stone of the Super Robot anime genre and its influence is still felt today. The opening theme, also titled Mazinger Z, is sung by Ichiro Mizuki.
Mazinger Z is a gigantic Super Robot, constructed with a fictitious metal called Chogokin Z (in the American translation, Super-Alloy Z), which is forged from a new element mined from a reservoir found only in the sediment of Japan's Mt. Fuji. The mecha was built by Professor Juzo Kabuto as a secret weapon against the forces of evil, represented in the series by the Mechanical Beasts (mecha used for evil purposes) of Dr Hell. The latter was the German member of a Japanese archeological team, which discovered ruins of a lost pre-Grecian civilization on an island named Bardos; the civilization was loosely based on the ancient Mycenae, and was called the Mikenese Empire in the series. One of their findings was that the Mikenese used an army of steel golems about 60 to 65 feet in height (compare with the Greek legend of Talos). Finding prototypes of those golems underground which could be remote-controlled and realizing their immense power on the battlefield, Dr. Hell goes insane and has all the other scientists of his research team killed. Except for Kabuto; the lone survivor escapes to Japan and attempts to warn the world of its imminent danger. Meanwhile, Dr. Hell establishes his headquarters on a mobile island which he sails around on, and plans to use the Mechanical Beasts to become the new ruler of the world. To counter this, Kabuto constructs Mazinger Z and manages to finish it just before being killed by a bomb planted by Hell’s right-hand man, Baron Ashura. As he is dying, he manages to inform his grandson Koji Kabuto about the robot and its use. Koji becomes the robot’s pilot, and from that point on battles both the continuous mechanical monsters, and the sinister henchmen sent by Doctor Hell in every episode.
In his Manga Works series, Go Nagai reveals that he had always loved Astro Boy and Gigantor as a child, and wanted to make his own robot anime. However, for the longest time he was unable to produce a concept that he felt didn't borrow too heavily from those two shows. One day, Nagai observed a traffic jam and mused to himself that the drivers in back would surely love a way to bypass the ones in front. From that thought came his ultimate inspiration: a giant robot that could be controlled from the inside, like a car. In his original concepts, the titular robot was Energer Z, which was controlled by a motorcycle that was driven up its back and into its head. However, with the sudden popularity of Kamen Rider, Nagai replaced the motorcycle with a hovercraft. He later redesigned Energer Z, renaming it Mazinger Z to evoke the image of a demon god (Ma, 魔, meaning demon and Jin, 神, meaning god). The motif of the Hover Pilder docking itself into Mazinger's head also borrows from Nagai's 1971 manga Demon Lord Dante (the prototype for his more popular Devilman), in which the titular giant demon has a human head (of Ryo Utsugi, the young man who merged with him) in his forehead. Interestingly, Koji Kabuto takes his surname (the Japanese word for a helmet) from the fact that he controls Mazinger Z from its head. (Wikipedia)