A Concert For Oscar! The spaceship piloted by Oscar, a friendly alien, crashes in Tommy's backyard and the two immediately strike up a friendship. Tommy introduces Oscar to his circle of friends: Professor Leonard, an eccentric scientist; Yucari, a formidable female martial arts practitioner and Peter, an aspiring musician. Yucari discovers Cesare, a villainous businessman, plans to turn the city park into a desert by killing all the plants with his special herbicide, then buying the property for next to nothing and turning it into a parking lot. Professor Leonard learns when music is played, the effects of the herbicide are spectacularly reversed, but when the crew is trapped in an abandoned tunnel, they may not be able to save the park before the mayor sells Caesar the deed.