mad as a box of frogs

Example: “My neighbor paints his garden gnomes neon pink; he's mad as a box of frogs, but lovely.”

Origin: Modern rather than traditional — British, and no older than the later twentieth century, despite sounding like something with centuries behind it. "Mad" carries its British sense of unhinged or eccentric, not the American sense of angry, and the image is precisely chosen: frogs confined in a box do not mill about but launch in unpredictable directions at random intervals, so the container is full of sudden, uncoordinated, purposeless motion with no way to anticipate what happens next. It belongs to a large and still-growing British family of comic madness similes built on the same template — mad as a hatter, mad as a March hare, mad as a bag of spanners, mad as a box of badgers — in which the comparison is expected to be inventive rather than inherited.