"Pigs is Pigs" by Ellis Parker Butler is a short story published in 1905. When railway agent Mike Flannery insists on charging the livestock rate for two guinea pigs rather than the pet rate—declaring "pigs is pigs"—a bureaucratic standoff ensues. The customer refuses delivery, leaving Flannery stuck with the animals in his office. As he awaits resolution from his superiors, an unexpected biological problem rapidly multiplies beyond his control, teaching him an unforgettable lesson about classification and common sense. (This is an automatically generated summary.)
These books are free to read. Each is in the public domain in the United States; check your own country's rules before you copy or share one.