A few clowns short of a circus.

A few fries short of a Happy Meal.

An experiment in Artificial Stupidity.

Dumber than a box of hair.

A few peas short of a casserole.

Doesn't have all his cornflakes in one box.

The wheel's spinning, but the hamster's dead.

One Fruit Loop shy of a full bowl.

One taco short of a combination plate.

A few feathers short of a whole duck.

The cheese slid off his cracker.

Body by Fisher, brains by Mattel.

Has an IQ of 2, but it takes 3 to grunt.

Warning: Objects in mirror are dumber than they appear.

Couldn't pour water out of a boot with instructions on the heel

He fell out of the Stupid tree and hit every branch on the way down.

An intellect rivaled only by garden tools.

As smart as bait.

Chimney's clogged.

Doesn't have all his dogs on one leash.

Doesn't know much but leads the league in nostril hair.

Elevator doesn't go all the way to the top floor.

Forgot to pay his brain bill.

Her sewing machine's out of thread.

His antenna doesn't pick up all the channels.

His belt doesn't go through all the loops.

If he had another brain, it would be lonely.

Missing a few buttons on his remote control.

No grain in the silo.

Receiver is off the hook.

Several nuts short of a full pouch.

Skylight leaks a little.

Slinky's kinked.

Surfing in Nebraska.

Too much yardage between the goal posts.

Big like ox, smart like tractor

A few sandwiches short of a picnic.