Sharp as a bag of wet mice. (Foghorn Leghorn)
Two small objects short of a collective noun.
As dumb as a mailbox
Elevator stops a couple floors short of the penthouse
Half a bubble out of plumb.
Republican.
Very close to my contribution:
Sharp as a bowling ball.
One for old times’ sake:
Not all there.
Not the sharpest peanut in the turd.
Has a mind like a steel colander
Sports reference: Thinks Wade Boggs is what you have to do to cross a river.
If brains were dynamite, he couldn’t blow his nose.
Dumber than a box of rocks.
Six cents short of a nickel.
He went out to lunch and stayed for happy hour.
He thinks “Shake Your Booty” is an Arab prince.
There was a power outage at the mall and he was stuck on an escalator for over two hours.
Not the brightest candle in the menorah.
Not the sharpest spoon in the drawer.
That’s my favorite.
A couple of tacos short of a combo plate.
(I heard Robin Williams use this one.)
Aint’ got the good sense God gave a cucumber.
My Great-Uncle Tom Mann (God rest hiz soul) specialized in the situation-specific “Damning with faint praise” version fo this. Shark Sandwich reminded me of this one:
Biggest piece of corn in the horse flop.
Other examples:
Smartest night-crawler in the can.
Wet behind the ears? He ain’t wet behind the ears! He’s the driest cow-patty in the pasture.
Wisest old sow in the briar patch.
Smartest man ever to come out of Ole’Miss.
*Disclaimer - these are all possibly much funnier if you can hear him saying them in his South-Georgia drawl. He’s gone twenty years at least, but I still can.
Hes a 45, playing on 33.
When God was giving out heads, he thought he heard beds, and asked for a big soft one.(cleaned up rather a lot)
Blunter than a blancmange slicer.
Sharp as a pound of wet leather. (also Foghorn Leghorn)
Duller than paint
Only occasionally fails at walking or chewing gum
Bright as the new moon
Can’t pour water out of a boot with instructions on the heel
He ain’t a flash in the pan, he’s just the pan
I like this one.
And the classic: The lights are on but no one’s home.
Well that’s what I was going to post. I think I heard it from Vicki Lawrence doing a Mama sketch on Carol Burnett.