A "fix-it-up chappie" named Sylvester McMonkey McBean appears and offers the Sneetches without stars the chance to have them with his Star-On machine, for three dollars. The treatment is instantly popular, but this upsets the original star-bellied Sneetches, as they are in danger of losing their special status. McBean then tells them about his Star-Off machine, costing ten dollars, and the Sneetches who originally had stars happily pay the money to have them removed in order to remain special. However, McBean does not share the prejudices of the Sneetches, and allows the recently starred Sneetches through this machine as well. Ultimately this escalates, with the Sneetches running from one machine to the next.
This continues until the Sneetches are penniless and McBean departs a rich man, amused by their folly. Despite his assertion that "you can't teach a Sneetch," the Sneetches learn from this experience that neither plain-belly nor star-belly Sneetches are superior, and they are able to get along and become friends.