What hit Stanley on his head?

Stanley is hit on the head by a pair of shoes—specifically, a stolen pair. Because he is caught with the stolen pair of shoes, he is charged with criminal action and sent to work at Camp Greenlake for rehabilitating young boys, though in reality it is for forced manual labor.
It is interesting, though, that he is hit by shoes because his father, the elder Stanley Yelnats, is working on developing a spray deodorizer for shoes, the solution to which Stanley stumbles across at Camp Greenlake, which effectively restores his family’s fortunes, in a very interconnected and interwoven way. So, while it seems like a horrible and unfortunate sequence of events, it ends up being very fortuitous for Stanley and his family.