Plural of mouse

The plural of mouse is mice. And so, the book reads, “T’was the night before Christmas and not a creature was stirring not even a mouse.”

Jules got me. She was about four or five. The illustration is of two mice. Aha! Plural mouses! She asked, “Which is the mouse? Which is the mice?” Of course the mices have names – Mouse and Mice! Every night she stopped me at this spot and asked her questions. I was stumped. One mouse, two mouse, but which are the mice? Which? Is the word “which” singular or plural? We never did clear it up. I remember to this day. And I am still at a loss for explanation. Some books – mercifully!!! – only illustrate one “mice” in the picture. It makes things eminently easier!