It can get worse, so beware of the following scenario.
Your toaster. Mice love toasters. A handy appliance otherwise, when it comes to mice their singular drawback becomes evident due to the necessity of their design. There it innocuously sits, a couple or more slots in the top with a cavernous interior where the right-sized rodent species can freely enter and exit at will, and once in these cute little vermin feel not only safe, but since the bottom of the device is full of bread crumbs, they can feed to their hearts content in presumed safety. That is, until