Very clever, cunning, or shrewd while appearing foolish or mad. People thought I was crazy when I told them my idea for massive social networking site—crazy like a fox, more like it!Our boss is crazy like a fox; her daredevil schemes always sound like they'll bankrupt us, but they invariably bring in a huge profit.
Seemingly foolish but actually very shrewd and cunning. For example, You think Bob was crazy to turn it down? He's crazy like a fox, because they've now doubled their offer . This usage gained currency when humorist S.J. Perelman used it as the title of a book (1944). [Early 1900s] .