Imagine a food and water dish with a port to screw in a water bottle. The bottle refills the water dish whenever the water level drops below the mouth of the bottle. To refill the bottle, you have to turn the dish upside down, which would cause any leftover food to spill out. The solution is to keep the food dish as a separate item, a detachable bowl that nests into a cavity next to the water dish. It keeps all the functionality of independent items, but appears as a single unit.