After his defeat by Goku while with the Red Ribbon army Dr. Gero went into seclusion working on several Androids for the sole purpose of killing and exacting revenge on Goku. Dr. Gero's first appearance in the Dragon Ball Z cartoon is on a distant island as a android accompanied with another android, Android 19. Dr. Gero hid his true identity from the Z-fighters calling himself Android 20. Bulma later reveals that Android 20 is Dr. Gero. After retreating from a losing battle with Piccolo he runs on foot back to his lab in order to activate Android 17 and Android 18. As soon as they were activated they disobeyed Dr. Gero's orders to kill the Z-fighters and instead killed him.
While fighting the Z-fighters Dr. Gero shows a unique skill only he and Android 19 posses. The ability to absorb energy from there opponents body or energy blasts is unique to there model of android.
Dr. Gero created these androids ( this list is not in any particular order)
- Android 19
- Android 18
- Android 17
- Android 16
- Android 14
- Android 13
Dr. Gero appears to be a feeble old man but he is actually a very powerful adversary. Although not as powerful as a Super Saiyan Dr. Gero was able to defeat Yamcha with ease. He has long white hair, energy absorbers on his palms, and a exposed brain to show that he is a brilliant scientist who turned himself into a immortal being.