The one about grammar and rodents...

In our part of the country, middle school students are taught the trick for identifying prepositions: anywhere a mouse can go. For example: 

a mouse can go inside your closet and induce your wrath by leaving his mousey mark on stacks of folded blankets and clothinga mouse can go around the live trap you bought in the hope that you wouldn't have to explain death to your children just yeta mouse can go  atop  the dog food bowl, enabling a veritable feast for his entire mousey familya mouse can go across the glue trap you laid out while thinking that at least he wouldn't die in front of the childrena mouse can go into the live trap finally, resulting in much celebrating and a short walk to a nearby open field for release into the wilda mouse can go behind your back and create more mice before you even walk back into the houseIn our part of the country, mice are as common as prepositions. However, finding either one in a definite manner can be challenging.
As one student pointed out: a mouse can go in a cat's mouth - does that mean "cat's mouth" is a preposition?
And as another student pointed out: why don't I just get a cat?
As every teacher and parent can attest, young people teach us as much as we teach them, as long as we are willing to listen.