Character Profile: Dr. Gero

Dr. Gero is the head scientist of the Red Ribbon Army and creates the first androids in the service of the Red Ribbon Army. Another scientist, Dr. Flappe is named as Android 8's creator. Daizenshuu 7 addresses this inconsistency by stating that Dr. Flappe and Dr. Gero were colleagues in charge of the Red Ribbon Army's Android Development Program. The Red Ribbon Army is not the primary reason for Dr. Gero's desire to create androids and cyborgs, as he reveals in GT that he always dreamed of replacing the entire human race with artificial beings even before Goku defeated the Red Ribbon Army.

After the Red Ribbon Army is defeated by Goku, Dr. Gero goes into hiding in his laboratory located in a mountain area north of North City. In this lab, he strives to create the ultimate fighting machine. Using an extremely intelligent tracking device disguised as a ladybug, he studies Goku and the Z Fighters for years, observing the fights Goku has with Tien Shinhan, King Piccolo, Piccolo, and the Saiyans Raditz, Nappa, and Vegeta.

Dr. Gero ceases the study of Goku's power when the Saiyan leaves for Namek, believing he had already compiled enough information; so he simply adjusts the androids' power levels to accommodate for Goku's expected power increase, not accounting for the power level of Goku's Super Saiyan form. Believing he had created the ultimate fighting machines, he finalizes his plans and constructed a series of Androids. While Dr. Gero is looking for fresh material for his experiments, he meets two notorious delinquents by chance, two siblings, a boy and a girl. He then kidnaps them and restructures them into Android 17 and Android 18.[1] However, the two became rebellious as they retain their human free will, so he deactivated them. According to Android 18, Dr. Gero destroyed all the other androids up to 15.

While constructing the Androids, Dr. Gero discovers a way to fuse together the cells from the strongest warriors to walk the Earth (Goku, Piccolo, Vegeta, Frieza, and King Cold), and tries to create a supreme fighting entity. After realizing that his project would take too long to complete, he decides to turn attention to other matters and leave his supercomputer from his lab to complete the ultimate being, who he names Cell.

To become immortal, Dr. Gero turns himself into an android, Android 20. The only human part of him as an android is his brain, which was transplanted into his android body by Android 19. Dr. Gero has his brain transferred into an energy-absorbing model Android rather than an infinite-powered model, which would have allowed him far greater power reserves. Android 18 hints that it may have been because he thinks that an energy-absorbing model android is easier to use as a host. Gero would later disguise his true identity by claiming that he is merely Android 20, and that Gero had died long ago.