This time it's a story.
When you think of cheese in illustrations or anime, don't you see holes in the cheese?
The hole is called "Cheese Eye" and is made from Emmental cheese, which is native to Switzerland. "Eyes" are large cavities (holes), and cheeses with even, clean circular holes are considered good cheeses.
Emmental cheese is matured using a bacterium called "propionate". The carbon dioxide gas (CO2) produced by this fungus creates holes in the cheese tissue.
From here on it's subjective.
I always thought that rats made holes in cheese. This image apparently comes from the American cartoon "Tom and Jerry"
Also, apparently rats don't eat much cheese. (Internet information)