#17 looks just like an ordinary human from the outside, but underneath is a psycho relentless killing robot. He has a twin sister (#18) which is just as deadly as himself. #17 is one of the most powerful and successful androids ever built by Dr Gero. Under the control of Dr Gero, #17 eventually has enough of being controlled and no freedom, hence he rebels and kills Dr Gero. This way the androids are set free and are free to do whatever they like. Killing and destroying things becomes his hobby, and he isn't willing to quit until the human race is completely wiped out. #17 is powered by a self generating energy source, which means he has unlimited energy.

In the original future, the #17 and #18 takes out most of the Z team including Piccolo, Vegeta, Krillin, Tien, where the only Z survivers are Trunks and Gohan (Gokou already died from a heart disease at that time). However, the androids are eventually taken out by Trunks after he arrives back from the past via the Time Machine.