Son Goku is the main character in all DBZ episodes. He is one of the most powerful beings in the universe. When he was sent here as a young Saiyan to destroy Earth, he took a deadly blow to the head and his memory was scrambled from being a Saiyan who will soon destroy Earth to the gaurdian of Earth. He fights many battles to save Earth and its people. Lets just hope he doesn't fail his job in one of the episodes.