It's fun to have the crowd cheer for you, especially if you are doing something smart. So if someone in class does exceptional work, shares a correct answer with the class when called upon, or just needs some praise, we cheer for them. The Snap-Crackle-Pop cheer goes like this:
After announcing Snap-Crackle-Pop, students snap their fingers once, rub the palms of their hands together(crac-kle), then clap(pop). It's short and sweet.