“Mad as a hatter”in other languages

Same idea, different pictures

English has a whole collection. Hatters really did go mad: the mercury used to treat felt poisoned them, and the phrase is older than Lewis Carroll's Mad Hatter. Off one's trolley comes from a trolley car that jumped its overhead wire; Afrikaans says the same, van sy trollie af. Mad as a box of frogs is a fairly recent British addition.

Animals and vegetables do the rest. Spanish is like a goat, como una cabra, the most unpredictable animal in the farmyard. English goes bananas, and Danish goes cucumber, at gå agurk, which is funny precisely because nothing is calmer than a cucumber.