The driving school test I just passed (with flying colors I'll have you know) had this in the middle of it:

"A frog is a term used to describe train car couplings."

Then, in the test section, right after something about how far behind another car you should stop at an intersection, would be "What is another term for a train coupling?"

I assume this was to make sure you read the test. I just cut & pasted the stuff into a text editor, so I could search for these odd duck questions when they came up.