3x38 - Dragon Ball Z: Dragon Box

After Goku arrives on Earth, the young man reveals his identity to him. The youth, who says his name is Trunks, is Vegeta's son. He says he has come from about 20 years in the future to warn them about Artificial Humans who will be appearing three years hence. Trunks goes on to say that the time machine he came back in was built by his mother. Even Goku is surprised to learn his mother's identity...