Le Passé de Son Goku

Goku and Gohan attend a reunion on Master Roshi's island, where Goku introduces his son to all of his old friends. The smiles quickly fade, however, as an unexpected visitor lands on the island, and for Goku the day becomes a reunion of a different kind. A powerful alien has arrived. It's Raditz: Goku's evil older brother! (Source: dbzepisode.org)