People are only now finding out the reason why the McNuggets pieces are different from each other - voila! Food. The McDonald's chain chooses to limit the shape options to only four options - and the company even has names for them.
There's the boot, the bone, the bell and the ball. The nuggets are a standardized shape and size to ensure consistent cooking times for food safety purposes at all McDonald's locations. Since all nuggets take the same amount of time to cook, it's easier and faster for staff to fill orders.