Idiomatic turns-of-phrase often reflect the culture or country in which they are used. We have already looked at some typically British phrases, like bats in the belfry and mad as a March hare.
In Australia, someone who is a little crazy is said to have a kangaroo loose in the paddock (a paddock is a small field), whereas someone who is more than a little crazy is mad as a gumtree full of galahs (a tree and bird species found only in Australia). The Australian equivalent of one sandwich short of a picnic is apparently one tinny short of a six-pack (of beer).
In the US, you can be out to lunch or, in more extreme circumstances, mad as a cut snake.
In Spain, you hear footsteps on the roof but in Sweden you are said to have gnomes in the loft.
If in English you can be not quite the shilling, in Germany they would say of you that all the cups are not in the cupboard. But can you imagine a more representative expression than the Dutch he was hit by a windmill?