Omni-man decides to invade DBZ Earth to try and conquer it. There are no Saiyajins available at the moment because they're out in an all-you-can-eat contest in universe 6 or something. Piccolo is out sleeping/meditating like he always does. Android 18 went shopping and 17 is out doing park ranger things.
Earth calls forward its mightiest human warrior, Krillin, to stop the mustached foreigner.