If you are on a mobile device and the play button is not displaying, go to the browser menu and click on "Request Desktop Site". Recommended browser (Google Chrome or Firefox)
Dragon Ball Z – The History of Trunks
The History of Trunks
Trunks from the alternate future where Goku has died and Androids terrorize the Earth. Amongst other things, it shows how Gohan trained Trunks, their fights with the Androids, and what inspired Trunks to go time traveling.