Getter Robo (ゲッターロボ Gettā Robo, typically romanized as Getter Robot in the various manga) is a Super Robot manga series created by Ken Ishikawa, as well as an anime series produced by Toei Animation. The series was broadcast on Fuji TV from April 4, 1974 to May 8, 1975, with a total of 51 episodes. Getter Robo is commonly mistaken for a Go Nagai work. While this isn't necessarily false, Go Nagai's involvement in the series was minimal, as the entirety of the original manga and subsequent manga sequels were both drawn and written by Ken Ishikawa.
The plot involves three strong-willed teenagers: martial artist Ryoma Nagare, homicidal psychopath Hayato Jin and fat Judoka Musashi Tomoe, who pilot three specially designed combat jets (Eagle, Jaguar, and Bear) which can be combined together into three different giant robots, Getter-1 (balanced and for flight combat), Getter-2 (fast and for ground combat), and Getter-3 (strong and for marine combat). They were assembled by Prof. Saotome, who conceived the Getter Robo project as a means of deep-space exploration. The Getter machine is powered by an energy source known as Getter Rays, which are the invisible manifestation of the pilot's willpower. It became instead Earth's first line of defense against the Dinosaur Empire, a civilization of reptile-like humanoids who evolved from the now-extinct dinosaurs that roamed the earth millions of years ago. They have lived many years underground after being forced to do so by getter ray radiation from space that did not affect the apes who evolved into humans; they now want to reclaim the Earth as theirs and destroy humanity.
The series was groundbreaking in the anime mecha genre: for the very first time, it introduced the concept of separate machines combining to form a Super Robot. Using three jets, Getter Robo could combine in three different ways to create three different versions of Getter Robo for different conditions and situations. This idea was originally discussed during the creation process for Mazinger Z (the first Super Robot to be piloted internally), but was dropped and then developed for Getter Robo. This idea of combination and transformation proved to be a very powerful concept that has been used in the super robot genre ever since. Also, by adding three pilots to the robot was able to add an element of teen drama, probably influenced by the already popular anime sci-fi team show Gatchaman (better known in the U.S. as Battle of the Planets, G-Force: Guardians of Space or Eagle Riders).