The life of Android 18 (I will refer to her as 18 so I don't have to type as much. So like I said the life of 18 started when she was activated by Android Dr. Gero. She and her evil brother 17 started off their life by killing the master and creature Dr. Gero. With him gone and out of there way they saw that there was another Android (16) that had not been activated. So being the people they were knowing that it well sucked to be asleep and not activated they activated android 16. So now that they were alive they would take over the world. With Vegeta and his cocky attitude he thought he could kill the androids by himself. So he challenged 18 and she well kicked his butt bad and almost killed him. So seeing that they z worriers and Vegeta and trunks were no match for 18 alone the androids (16, 17, and 18) moved on in search of Goku but Krillen tried to stop them and they didn't responded but with 18 telling him to get his friends some senzu beans and gave him a kiss. But what the androids did not know was that Goku had just had a fight with androids 19 (god knows what) and 20 (Dr. Gero) and had a hart virus attack during the middle. So Yamcha took Goku to his house were the medicine for the hart virus was while the new supersaiyan Vegeta took care of 19 and 20 (Dr. Gero) got away and then activated 17 and 18 and then all what I told you happen and now they are after Goku (witch is sick from the hart virus and in bed at his house. Now for a awhile the androids are not in the show much and it focuses on cell as he makes his first appearance. Then after awhile Cell and android 17 get in a fight and 17 is absorbed. So then 18 and 16 run while Tien keeps Cell busy and after that there is a lot of people reaching new stages and trying to beat Cell and Vegeta would have done it but he allowed Cell to absorb 18 for the Challenge witch takes 18 out of the show for a while. But later when Supersaiyan 2 Gohan is beating on Cell he spits 18 back out, but she is knocked out for the whole Cell saga.