In "A & P," why does Sammy see one woman as a "witch" and the others as "sheep" and the store as a "pinball machine"?
Sammy describes them in this way because it reflects his attitude. Updike uses the first person point of view and the present tense to put the reader inside Sammy's head. We are seeing the events unfold from the mind of a rather uneducated, discontent teenager. His frustration and angst are clear when he refers to the one shopper as a witch - "if she'd been born at the right time they would have burned her over in Salem." Comments like these perfectly reflect his hatred of not only the customers but his job too.
Sammy refers to the store as a pinball machine because, as a nineteen year old, that is probably the most natural simile that comes to his mind. Plus, it reflects his anticipation at what watching them travel down the various aisles.
Sammy also refers to the women shoppers as sheep, for they seem to blindly follow along on their paths throughout the store and their lives. As a single young man, Sammy doesn't have that routine or sense of purpose in his life. Even though he ridicules the women in the store and Stokesie (his coworker) and Lengel (his boos), he fails to see that at least they all have purposes. The women are raising families, Stokesie is married and providing for his family, and Lengel is running a business. But Sammy himself is just an angry young man who makes a foolish ploy at trying to impress the girls and gets fired.