America - Front
America - Back
Enter Commander Keen, the alter-ego of eight-year-old boy genius Billy Blaze. After refusing to eat his vegetables, Billy is sent to bed by his parents. He falls asleep, only to awaken in a strange vegetable kingdom... He discovers this kingdom is controlled by the evil potato king, Boobus Tuber, who has imprisoned many other sleeping children as well! In the dream world, Keen does not have his trademark raygun and pogo stick, but has to defend himself with "Flower Power" seeds that temporarily turn enemies into flowers.
(information paraphrased from Wikipedia)
Download the demo from Commander-Keen.com.