In S.E. Hinton's novel The Outsiders, the protagonist and narrator is a teenage boy named Ponyboy Curtis. In this novel, the word "crazy" usually means "to be very interested in something." For example, his brother Sodapop is called "horsecrazy" because "he's always hanging around stables and rodeos." Another of Ponyboy's friends, Johnny, "was crazy about drag races." Ponyboy himself says that he and his brothers were "crazy about chocolate stuff." A look at the word "crazy" in the novel will not find Ponyboy being called "crazy" with respect to anything other than chocolate.
Just before the big fight between the Greasers and the Socials, Ponyboy was in a weakened condition and was not physically prepared for the upcoming rumble. His brother Darry advised him not to fight, but Ponyboy was determined to take part in the fight because he wanted to participate in taking vengeance upon the Socials. Still, I'm not sure wanting to fight when one is not physically prepared to fight qualifies Ponyboy as "crazy."
After the big fight between the Greasers and the Socials, during which Ponyboy gets kicked in the head, he is described as being "delirious." Ponyboy also declares that he "started running into things, like the door, and kept tripping over the coffee table and losing things." Ponyboy's schoolwork also starts to suffer.
Thus, if Ponyboy is "crazy," his craziness amounts to a love of chocolate, a desire to fight when he is not physically fit to fight, and the after-effects of a concussion. Otherwise, Ponyboy is perhaps the most sane person in Hinton's novel.