The story begins when a meteor falls in Onett, a small American town. Ness, the main character, heads outside with his dog to investigate. At the crash site, he learns from Buzz Buzz, a bee-like creature from the future, that he must collect eight melodies to defeat Giygas, an evil overlord who wages war against the earth.
The game then follows Ness and his friends as he travels from location to location, battling mushrooms, taxis, UFOs, and hippies. He rescues Paula, a magically-adept girl held captive by a cult outside Tucson, and meets up with Jeff, a boy from an English boarding school. The group's fourth member is Poo, prince of the Asian country of Dalaam.
The game's principle antagonists are the Starmen, Giygas' warriors, also sent back from the future, who make continual mischief by stealing important items, including Poo's Sword of Kings, the Suporma (a device created by the child genius Orange Kid), and the Shyness Book from the Onett library (needed to communicate with the Tenda village). Allied with the Starmen is Pokey Minch, Ness' overweight neighbor, who goes from playing tricks on Ness to becoming Giygas' right-hand man.
- Ness: The silent protagonist who wields a baseball bat.
- Paula: A psychically-adept girl who wields frying pans.
- Jeff: An inventor from Winters who creates useful machines from junk.
- Poo: Prince of the eastern kingdom of Dalaam who can only wield of the Sword of Kings.
- Pokey: Ness' next door neighbor and the game's primary antagonist.