put downs

Some drink from the fountain of knowledge; he only gargled.

One Froot Loop shy of a full bowl.

Not the brightest bulb on the Xmas tree

A donut short of being a cop

A few feathers short of a whole duck.

From the British Army? Are you sure you're not from the Salvation Army?

Which village is missing its idiot?.

A Titanic intellect ... In a world full of icebergs

A few clowns short of a circus

A few beads short in her rosary.