OK, so here is a nice one that took me several months to collect...
You know the expression in English, a third wheel? or is it a fifth wheel? well, any unnecessary wheel. So I learned a few month ago that in Chinese the same person is called a "light-bulb", and that is because when you want some privacy with someone, some intimate privacy with that special someone, than a light emitting glass device is not exactly what you want on your side...
That was cool, but it was not Japanese. Yesterday I learnt the same expression but this time, the Japanese version of it.
Reading: kingyo no fun
Meaning: sort of the same as a third/fifth wheel in English.
Literally: goldfish droppings
Well, apparently when a goldfish poos, his poo is dangling around behind him for quite some time. So this expression means a person who tags along; hanger-on; a person who follows someone around like a shadow; clingy person.
So there, that's an image for you!