A few beers short of a six-pack.
A few clowns short of a circus.
A few feathers short of a whole duck.
A few fries short of a Happy Meal.
A few peas short of a casserole.
A few pickles short of a jar.
A hole in his bag of marbles.
A living example of artificial intelligence.
About as bright as a black hole.
About as sharp as a bowling ball.
About as sharp as jello.
About as smart as live bait.
All foam, no beer.
All sail and no boat.
An experiment in Artificial Stupidity.
An intellect rivaled only by that of garden tools.
As sharp as a marble.
As smart as bait.
Chimney’s clogged.
Doesn’t have all his cornflakes in one box.
Doesn’t have all his dogs on one leash.
Doesn’t know which side of the toast the butter is on.
Dumber than a box of hair.
Forgot to pay his brain bill.
Grease spot on the driveway of life.
Her elevator doesn’t go all the way to the top floor.
His Slinky’s kinked.
Knitting with only one needle.
Not the brightest color…in the crayon box.
One Froot Loop shy of a full bowl.
One sandwich short of a picnic.
One taco short of a combination plate.
She’s sharp as a marble!
Strong, like a Bear…Smart, like a Tractor.
Studies hard for blood tests.
The cheese slid off his cracker.
The wheel’s spinning, but the hamster’s dead.