The First Cash Register, Cancel!

In a faraway city on a faraway street stands the most ordinary supermarket. However, something terrifying and incredible happens there every now and then. Sometimes the cash register almost consumes the cashier, sometimes a beef carcass wanders the meat department... after closing, sometimes spoiled products attack a complaining customer, scaring them to death... In short, the further it goes, the scarier it gets!
But the scariest thing is that the faraway city may turn out to be your own. And the faraway street now begins in your yard. And the "most ordinary" supermarket is right outside your windows. And the local guard claims that he invented you - specifically you! - once out of boredom.
It seems he is in trouble. It seems this is serious. It seems you both will have to deal with the intertwined realities.
For middle school age.