Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot (Captain Underpants #12)

George and Harold, and their doubles, Yesterday George and Yesterday Harold, have a good thing going. Two of them go to school, while the other two hide in the tree house and play video games all day -- then they switch! But when their malicious gym teacher, Mr. Meaner, creates a method of mind control that turns their fellow students into attentive, obedient, perfect children, the future of all humanity will be in their hands!