There are two timelines in the world of DBZ. In one timeline, Gokou died from a heart disease three years before two Androids named Junanagou and Juhachigou show up to destroy the world. When they do appear, the other Z-fighters are killed, as they are not strong enough to win. Only Trunks survives and and eventually kills them, but then he is murdered by Cell. For more information, go to the Trunks Special.

In the other timeline, Gokou's heart disease comes while he is fighting Androids 19 and 20. Trunks had already given him some medicine, so Gokou survived. Also, three other Androids made their appearance. They were Jurokugou, Junanagou, and Juhachigou. They really only had interest in Gokou, so all the Z-fighters survived. And when Cell showed up, everyone was much stronger and they were able to stay alive. Gohan finally killed Cell with a one-handed Kamehameha. This enables Trunks to stay alive and go back to the future and kill the Androids and Cell, changing history. This is evident because he later shows up in the series as Chibi Trunks and grows up to be the GT Trunks we all know and love.