Getter Robo (ゲッターロボ - Gettâ Robo) is a Super Robot anime series created by Go Nagai and Ken Ishikawa and produced by Toei Animation. The series was broadcast on NET (now TV Asahi) from April 4, 1974 to May 8, 1975, with a total of 51 episodes. This anime series featured the first heroic giant robot to combine from individual parts.
The plot involves three strong-willed teenagers: soccer player and martial artist Ryoma Nagare, rebel loner Hayato Jin and Judo master Musashi Tomoe, who pilot three specially designed combat jets which can be combined together in different forms to form three different kinds of giant robots, Getter-1 (used for aerial combat), Getter-2 (for land-based conflicts), and Getter-3 (for undersea battles). They were assembled by Prof. Saotome, who conceived the Getter Robo project as Earth's first line of defense against the Dinosaur Empire, which is 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, and 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, but was dropped and then developed for Getter Robo. This combination idea proved to be a very powerful concept that has been used in the super robot genre ever since. (Wikipedia)