My Dad used ot admonish us: "What do you think you're on? Your fathers' yacht, or your grannys' gunboat?"

There's 'Dim as a Toc-H lamp;, 'Daft as a brush', 'Poor as a church mouse' and the all-time classic: "If brains were elastic, you wouldn't have enough for a frogs' jockstrap!"

Also, my great-grandmother once remarked of a female neighbour that she was 'no better than she should be'. Never figured that one out, but suspect unkindness.