Dragon Ball Z - episode 67 - 13 Nov, 1990

With Recoome beaten by one punch, the remaining two Ginyu Force members, Burter and Jeice, fight against Goku, but none of their speed attacks work against him. They try to hit him, but their punches seem to go through Goku. He is dodging so fast that it appears he isn't even moving. Vegeta believes that Goku has become the legendary Saiyan warrior, the Super Saiyan. If this is true, Goku would be the first Super Saiyan in millennia. (Source: Wikipedia)