Dr. Gero transformed himself into a cyborg by implanting his brain into a robotic body. He first appeared with Android #19, intending to kill Goku. After #19 was destroyed by Vegeta, Dr. Gero fled out of fear and planned to activate Androids #17 and #18. However, once activated, they rebelled against their creator. Android #17 kicked off Dr. Gero's head and crushed it.
Following the defeat of the Red Ribbon Army by Goku, Dr. Gero retreated to his hidden laboratory in a mountainous region north of North City. There, he aimed to create the ultimate fighting machine. Using an advanced tracking device disguised as a ladybug, he observed Goku and the Z Fighters for years, studying their battles against Tien Shinhan, King Piccolo, Piccolo, and the Saiyans Raditz, Nappa, and Vegeta.
Dr. Gero stopped monitoring Goku's power when the Saiyan left for Namek, believing he had gathered sufficient data. He adjusted the androids' power levels to match Goku's expected increase, but failed to account for the power of Goku's Super Saiyan form. Convinced he had created the ultimate fighters, he finalized his plans and constructed several androids. Android 16 was modeled after Gero's deceased son, a high-ranking Red Ribbon soldier killed by an enemy bullet. Out of affection, Gero made him powerful but gentle to avoid destruction in battle.
While searching for experimental subjects, Dr. Gero encountered two notorious delinquents, a brother and sister, whom he kidnapped and restructured into Androids #17 and #18. However, due to retaining their human free will, they became rebellious, leading Dr. Gero to deactivate them.
In Dragon Ball GT, Dr. Gero collaborated with Dr. Myu to create Super 17, who ultimately turned on and killed both of them.
