Dr. Gero (a.k.a Android 20) is the brilliant scientist in the Red Ribbon Army. After the Red Ribbon Army's defeat in the hands of Goku, Gero retreated to his mountain laboratory to plot his revenge with his Androids (Artificial Humans). Not until he reached Android 19 did he create an obedient, bloodthirsty servant. Gero then had #19 transplant his brain into an android body, thus turning himself into an Android and preventing him from dying of old age. After his second defeat at the hands of the Z Fighters, Gero retreated to his lab to activate Androids 17 and 18, who rebelled and killed the doctor. Though Gero died, he left behind Android 13, Android 14, Android 15, and his best creation known, Cell. He returns in Dragon Ball GT with Dr.Myuu and together they create another Android 17. They make the two Androids fuse to create Super 17.