Heres a few I found doing a search at google.com:
A beer short of a six pack.
A brick short of a load.
A couple of eggs shy of a dozen.
A couple of gallons short of a full tank.
A few ants short of a picnic.
A few bricks short of a pile.
A few bricks short of a wall.
A few cards short of a deck.
A few clowns short of a circus.
A few feathers short of a whole duck.
A few of sheep short of an orgy.
A few peas short of a casserole.
A few tomatoes short of a good thick sauce.
A few trucks short of a convoy.
A fortune cookie short of a Chinese dinner.
A pepperoni short of a pizza.
A photographic memory but with the lens cover glued on.
A sandwich short of a picnic.
About as bright as a burnt out 20 watt light bulb.
An experiment in Artificial Stupidity.
An intellect rivalled only by garden tools.
As much use as a hedgehog in a condom factory.
As much use as a one-legged man at an ass-kicking contest.
As much use as an ashtray on a motorcycle.
As quick as a tortoise on Prozac.
As smart as bait.
As useful as a screen door on a submarine.
As useful as a wooden frying pan.
As useful as tits on a bull.
Bright as Alaska in December.
Couldn't pour water out of a boot with instructions on the heel.
Doesn’t have both oars in the water.
Doesn't have all his cornflakes in one box.
Doesn't have all the dots on his dice.
Donated his body to science before he was done using it.
Dumb as a corn cob.
Dumb as a stump.
Dumber than a bag of hammers.
Dumber than a bag of rocks.
Elevator don't quiet make the top floor.
Fell out of the family tree.
Forgot to pay his brain bill.
Goes surfing in Nebraska.
Golf bag doesn’t have a full set of irons.
Got into the gene pool when the lifeguard wasn’t watching.
Gross ignoramus--144 times worse than a normal ignoramus.
Has an IQ of 2, but it takes 3 to grunt.
Has delusions of adequacy.
Has two brains, one's lost and the other is out looking for it.
He had a little too much chlorine in his gene pool.
He is so dumb, he would look for a wishbone in a soft-boiled egg.
He is so dumb, the only thing he ever read was an eye-chart.
He played too much without a helmet.
He’s got a mind like a steel trap, rusted shut.
He's got a leak in his think-tank.
He's got a mind like a steel sieve.
He's got his feet firmly planted 3 feet above the ground.
He's not the sharpest knife in the drawer.
He's so dense light bends around him.
His belt doesn't go through all the loops.
His cheese has slipped off his cracker.
His porch light ain't on.
If brains were chocolate, he wouldn't have enough to fill an M&M.
If brains were dynamite, he wouldn't have enough to blow his nose.
If brains were dynamite, he wouldn’t have enough to blow his hat off.
If brains were gasoline, he couldn't ride a moped around a fruit loop.
If brains were taxed, he’d get a rebate.
If he had a brain, he'd be dangerous.
If he had another brain, it would be lonely.
If he were any more stupid, he’d have to be watered twice a week.
If stupid were a talent, he would be considered gifted.
If you gave him a penny for his thoughts, you'd get change back.
If you stand close enough to 'em you can hear the ocean.
Isn’t firing on all 6 cylinders.
Isn’t firing on all thrusters.
It's hard to believe that he beat out half a billion other sperm.
Kangaroo loose in the top paddock.
Like a pair of children’s scissors, bright and colourful, but not too sharp.
Million dollar body and a 2 dollar engine.
Mind is in neutral, body is in gear.
Mind like a rubber bear trap.
Needing a few screws tightened.
Not firing with all spark plugs.
Not the brightest light in the harbour.
Not the brightest light on the Christmas tree.
Not the sharpest hook in the tackle box.
Not the sharpest pencil in the box.
Off his rocker.
On/off switch is broken in the off position.
One Fruit Loop shy of a full bowl.
One neuron short of a synapse.
One taco short of a combination plate.
One tit short of an udder.
One turbine short of an airplane.
One-celled organisms out score him in IQ tests.
Prime candidate for natural deselection.
Proof that evolution CAN go in reverse.
Requires directions to lay sod.
Room temperature IQ.
Running about a quart low.
Running on empty.
Sets the lowest possible goals, and consistently fails to achieve them.
Sharp as a bowling ball.
She is so dumb, she couldn't tell which way an elevator was going if she had two guesses.
She's not tied too tight to the pier.
Some drink from the fountain of knowledge but he just gargled.
Strong like bear, smart like tractor.
Takes him 1-1/2 hours to watch 60 minutes.
The elevator is stuck between floors.
The lights are flashing, the gate is down, but the train isn’t coming.
The lights are on, but nobody is home.
The wheel is turning but the hamster is dead.
The wheel's spinning, but the hamster's dead.
Too dumb to pull his head in before he shuts the window.
Too many yards between the goal posts.
Two hub caps short of a Buick.
Warning--Objects in mirror are dumber than they appear.
Was left on the tilt-a-whirl too long as a baby.
Would be out of her depth in a mud puddle.
You're the flower of my life (you blooming idiot).
You can't call him an idiot, you'll insult all the idiots in the world.
TR
